;; prolog.el --- major mode for editing and running Prolog (and Mercury) code

;; Copyright (C) 1986, 1987, 1997, 1998, 1999, 2002, 2003 Free Software Foundation, Inc.

;; Authors: Emil strm <emil_astrom@hotmail.com>
;;          Milan Zamazal <pdm@freesoft.cz>
;;          Stefan Bruda <bruda@ubishops.ca>     <-- current maintainer
;;          (see below for more details)
;; Keywords: prolog major mode sicstus swi mercury

(defvar prolog-mode-version "1.3"
  "Prolog mode version number")

;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;; Original author: Masanobu UMEDA <umerin@mse.kyutech.ac.jp>
;; Parts of this file was taken from a modified version of the original
;; by Johan Andersson, Peter Olin, Mats Carlsson, Johan Bevemyr, Stefan
;; Andersson, and Per Danielsson (all SICS people), and Henrik Bkman
;; at Uppsala University, Sweden.
;;
;; Some ideas and also a few lines of code have been borrowed (not stolen ;-)
;; from Oz.el, the Emacs major mode for the Oz programming language,
;; Copyright (C) 1993 DFKI GmbH, Germany, with permission.
;; Authors: Ralf Scheidhauer and Michael Mehl ([scheidhr|mehl]@dfki.uni-sb.de)
;;
;; More ideas and code have been taken from the SICStus debugger mode
;; (http://www.csd.uu.se/~perm/source_debug/index.shtml -- broken link
;; as of Mon May 5 08:23:48 EDT 2003) by Per Mildner.
;;
;; Additions for ECLiPSe and other helpful suggestions: Stephan Heuel
;; <heuel@ipb.uni-bonn.de>

;;; Commentary:
;;
;; This package provides a major mode for editing Prolog code, with
;; all the bells and whistles one would expect, including syntax
;; highlighting and auto indentation.  It can also send regions to an
;; inferior Prolog process.
;;
;; The code requires the comint, easymenu, info, imenu, and font-lock
;; libraries. These are normally distributed with GNU Emacs and
;; XEmacs.

;;; Installation:
;;
;; Insert the following lines in your init file--typically ~/.emacs
;; (FSF Emacs and XEmacs <21.4), or ~/.xemacs/init.el (XEmacs
;; 21.4)--to use this mode when editing Prolog files under Emacs:
;;
;; (setq load-path (cons "/usr/lib/xemacs/site-lisp" load-path))
;; (autoload 'run-prolog "prolog" "Start a Prolog sub-process." t)
;; (autoload 'prolog-mode "prolog" "Major mode for editing Prolog programs." t)
;; (autoload 'mercury-mode "prolog" "Major mode for editing Mercury programs." t)
;; (setq prolog-system 'swi)  ; optional, the system you are using;
;;                            ; see `prolog-system' below for possible values
;; (setq auto-mode-alist (append '(("\\.pl$" . prolog-mode)
;;                                 ("\\.m$" . mercury-mode))
;;                                auto-mode-alist))
;;
;; where the path in the first line is the file system path to this file.
;; MSDOS paths can be written like "d:/programs/emacs-19.34/site-lisp". 
;; Note: In XEmacs, either `/usr/lib/xemacs/site-lisp' (RPM default in
;; Red Hat-based distributions) or `/usr/local/lib/xemacs/site-lisp'
;; (default when compiling from sources) are automatically added to
;; `load-path', so the first line is not necessary provided that you
;; put this file in the appropriate place.
;;
;; The last s-expression above makes sure that files ending with .pl
;; are assumed to be Prolog files and not Perl, which is the default
;; Emacs setting. If this is not wanted, remove this line. It is then
;; necessary to either
;;
;;  o  insert in your Prolog files the following comment as the first line:
;;
;;       % -*- Mode: Prolog -*-
;;
;;     and then the file will be open in Prolog mode no matter its 
;;     extension, or
;;
;;  o  manually switch to prolog mode after opening a Prolog file, by typing 
;;     M-x prolog-mode.
;;
;; If the command to start the prolog process ('sicstus', 'pl' for SWI
;; prolog, etc.) is not available in the default path, then it is
;; necessary to set the value of the environment variable EPROLOG to a
;; shell command to invoke the prolog process.  In XEmacs and Emacs
;; 20+ you can also customize the variable `prolog-program-name' (in
;; the group `prolog-inferior') and provide a full path for your
;; Prolog system (swi, scitus, etc.).
;;
;; Note: I (Stefan, the current maintainer) work under XEmacs.  Future
;;   developments will thus biased towards XEmacs (OK, I admit it, I
;;   am biased towards XEmacs in general), though I will do my best
;;   to keep the FSF Emacs compatibility.  So if you work under Emacs
;;   and see something that does not work do drop me a line, as I
;;   have a smaller chance to notice this kind of bugs otherwise.

;; Changelog:

;; Version 1.3:
;;  o  Info-follow-nearest-node now called correctly under Emacs too
;;     (thanks to Nicolas Pelletier).  Should be implemented more
;;     elegant (i.e., without compilation warnings) in the future.
;; Version 1.2:
;;  o  Another prompt fix, still in SWI mode (people seem to have
;;     changed the prompt of SWI Prolog).
;; Version 1.1:
;;  o  Fixed dots in the end of line comments causing indentation
;;     problems.  The following code is now correctly indented (note
;;     the dot terminating the comment):
;;        a(X) :- b(X),                   
;;            c(X).                  % comment here.
;;        a(X).
;;     and so is this (and variants):
;;        a(X) :- b(X),                   
;;            c(X).                  /* comment here. */
;;        a(X).
;; Version 1.0:
;;  o  Revamped the menu system.
;;  o  Yet another prompt recognition fix (SWI mode).
;;  o  This is more of a renumbering than a new edition.  I promoted
;;     the mode to version 1.0 to emphasize the fact that it is now
;;     mature and stable enough to be considered production (in my
;;     opinion anyway).
;; Version 0.1.41:
;;  o  FSF Emacs compatibility fixes.
;; Version 0.1.40:
;;  o  prolog-get-predspec is now suitable to be called as
;;     imenu-extract-index-name-function.  The predicate index works.
;;  o  Since imenu works now as advertised, prolog-imenu-flag is t
;;     by default.
;;  o  Eliminated prolog-create-predicate-index since the imenu
;;     utilities now work well.  Actually, this function is also
;;     buggy, and I see no reason to fix it since we do not need it
;;     anyway.
;;  o  Fixed prolog-pred-start, prolog-clause-start, prolog-clause-info.
;;  o  Fix for prolog-build-case-strings; now prolog-upper-case-string
;;     and prolog-lower-case-string are correctly initialized, 
;;  o  Various font-lock changes; most importantly, block comments (/*
;;     ... */) are now correctly fontified in XEmacs even when they
;;     extend on multiple lines.
;; Version 0.1.36: 
;;  o  The debug prompt of SWI Prolog is now correctly recognized.
;; Version 0.1.35: 
;;  o  Minor font-lock bug fixes.


;;; Code:

(eval-when-compile
  (require 'compile)
  (require 'font-lock)
  ;; We need imenu everywhere because of the predicate index!
  (require 'imenu)
  ;)
  (require 'info)
  (require 'shell)
  )

(require 'comint)
(require 'easymenu)


(defgroup prolog nil
  "Major modes for editing and running Prolog and Mercury files."
  :group 'languages)

(defgroup prolog-faces nil
  "Prolog mode specific faces."
  :group 'font-lock)

(defgroup prolog-indentation nil
  "Prolog mode indentation configuration."
  :group 'prolog)

(defgroup prolog-font-lock nil
  "Prolog mode font locking patterns."
  :group 'prolog)

(defgroup prolog-keyboard nil
  "Prolog mode keyboard flags."
  :group 'prolog)

(defgroup prolog-inferior nil
  "Inferior Prolog mode options."
  :group 'prolog)

(defgroup prolog-other nil
  "Other Prolog mode options."
  :group 'prolog)


;;-------------------------------------------------------------------
;; User configurable variables
;;-------------------------------------------------------------------

;; General configuration

(defcustom prolog-system nil
  "*Prolog interpreter/compiler used.
The value of this variable is nil or a symbol.
If it is a symbol, it determines default values of other configuration
variables with respect to properties of the specified Prolog
interpreter/compiler.

Currently recognized symbol values are:
eclipse - Eclipse Prolog
mercury - Mercury
sicstus - SICStus Prolog
swi     - SWI Prolog"
  :group 'prolog
  :type '(choice (const :tag "SICStus" :value sicstus)
                 (const :tag "SWI Prolog" :value swi)
                 (const :tag "Default" :value nil)))
(make-variable-buffer-local 'prolog-system)

;; NB: This alist can not be processed in prolog-mode-variables to
;; create a prolog-system-version-i variable since it is needed
;; prior to the call to prolog-mode-variables.
(defcustom prolog-system-version
  '((sicstus  (3 . 6))
    (swi      (0 . 0))
    (mercury  (0 . 0))
    (eclipse  (3 . 7)))
  "*Alist of Prolog system versions.
The version numbers are of the format (Major . Minor).")


;; Indentation

(defcustom prolog-indent-width tab-width
  "*The indentation width used by the editing buffer."
  :group 'prolog-indentation
  :type 'integer)  

(defcustom prolog-align-comments-flag t
  "*Non-nil means automatically align comments when indenting."
  :group 'prolog-indentation
  :type 'boolean)

(defcustom prolog-indent-mline-comments-flag t
  "*Non-nil means indent contents of /* */ comments.
Otherwise leave such lines as they are."
  :group 'prolog-indentation
  :type 'boolean)

(defcustom prolog-object-end-to-0-flag t
  "*Non-nil means indent closing '}' in SICStus object definitions to level 0.
Otherwise indent to `prolog-indent-width'."
  :group 'prolog-indentation
  :type 'boolean)

(defcustom prolog-left-indent-regexp "\\(;\\|\\*?->\\)"
  "*Regexp for character sequences after which next line is indented.
Next line after such a regexp is indented to the opening paranthesis level."
  :group 'prolog-indentation
  :type 'regexp)

(defcustom prolog-paren-indent 4
  "*The indentation increase for parenthesis expressions.
Only used in ( If -> Then ; Else) and ( Disj1 ; Disj2 ) style expressions."
  :group 'prolog-indentation
  :type 'integer)

(defcustom prolog-parse-mode 'beg-of-clause
  "*The parse mode used (decides from which point parsing is done).
Legal values:
'beg-of-line   - starts parsing at the beginning of a line, unless the
                 previous line ends with a backslash. Fast, but has
                 problems detecting multiline /* */ comments.
'beg-of-clause - starts parsing at the beginning of the current clause.
                 Slow, but copes better with /* */ comments."
  :group 'prolog-indentation
  :type '(choice (const :value beg-of-line)
                 (const :value beg-of-clause)))

;; Font locking

(defcustom prolog-keywords
  '((eclipse
     ("use_module" "begin_module" "module_interface" "dynamic"
      "external" "export" "dbgcomp" "nodbgcomp" "compile"))
    (mercury
     ("all" "else" "end_module" "equality" "external" "fail" "func" "if"
      "implementation" "import_module" "include_module" "inst" "instance"
      "interface" "mode" "module" "not" "pragma" "pred" "some" "then" "true"
      "type" "typeclass" "use_module" "where"))
    (sicstus
     ("block" "dynamic" "mode" "module" "multifile" "meta_predicate"
      "parallel" "public" "sequential" "volatile"))
    (swi
     ("discontiguous" "dynamic" "ensure_loaded" "export" "export_list" "import"
      "meta_predicate" "module" "module_transparent" "multifile" "require"
      "use_module" "volatile"))
    (t
     ("dynamic" "module")))
  "*Alist of Prolog keywords which is used for font locking of directives."
  :group 'prolog-font-lock
  :type 'sexp)

(defcustom prolog-types
  '((mercury
     ("char" "float" "int" "io__state" "string" "univ"))
    (t nil))
  "*Alist of Prolog types used by font locking."
  :group 'prolog-font-lock
  :type 'sexp)

(defcustom prolog-mode-specificators
  '((mercury
     ("bound" "di" "free" "ground" "in" "mdi" "mui" "muo" "out" "ui" "uo"))
    (t nil))
  "*Alist of Prolog mode specificators used by font locking."
  :group 'prolog-font-lock
  :type 'sexp)

(defcustom prolog-determinism-specificators
  '((mercury
     ("cc_multi" "cc_nondet" "det" "erroneous" "failure" "multi" "nondet"
      "semidet"))
    (t nil))
  "*Alist of Prolog determinism specificators used by font locking."
  :group 'prolog-font-lock
  :type 'sexp)

(defcustom prolog-directives
  '((mercury
     ("^#[0-9]+"))
    (t nil))
  "*Alist of Prolog source code directives used by font locking."
  :group 'prolog-font-lock
  :type 'sexp)


;; Keyboard

(defcustom prolog-electric-newline-flag t
  "*Non-nil means automatically indent the next line when the user types RET."
  :group 'prolog-keyboard
  :type 'boolean)

(defcustom prolog-hungry-delete-key-flag nil
  "*Non-nil means delete key consumes all preceding spaces."
  :group 'prolog-keyboard
  :type 'boolean)

(defcustom prolog-electric-dot-flag nil
  "*Non-nil means make dot key electric.
Electric dot appends newline or inserts head of a new clause.
If dot is pressed at the end of a line where at least one white space
precedes the point, it inserts a recursive call to the current predicate.
If dot is pressed at the beginning of an empty line, it inserts the head
of a new clause for the current predicate. It does not apply in strings
and comments. 
It does not apply in strings and comments."
  :group 'prolog-keyboard
  :type 'boolean)

(defcustom prolog-electric-underscore-flag nil
  "*Non-nil means make underscore key electric.
Electric underscore replaces the current variable with underscore.
If underscore is pressed not on a variable then it behaves as usual."
  :group 'prolog-keyboard
  :type 'boolean)

(defcustom prolog-electric-tab-flag nil
  "*Non-nil means make TAB key electric.
Electric TAB inserts spaces after parentheses, ->, and ;
in ( If -> Then ; Else) and ( Disj1 ; Disj2 ) style expressions."
  :group 'prolog-keyboard
  :type 'boolean)

(defcustom prolog-old-sicstus-keys-flag nil
  "*Non-nil means old SICStus Prolog mode keybindings are used."
  :group 'prolog-keyboard
  :type 'boolean)

;; Inferior mode

(defcustom prolog-program-name
  '(((getenv "EPROLOG") (eval (getenv "EPROLOG")))
    (eclipse "eclipse")
    (mercury nil)
    (sicstus "sicstus")
    (swi "pl")
    (t "prolog"))
  "*Alist of program names for invoking an inferior Prolog with `run-prolog'."
  :group 'prolog-inferior
  :type 'sexp)

(defcustom prolog-program-switches
  '((sicstus ("-i"))
    (t nil))
  "*Alist of switches given to inferior Prolog run with `run-prolog'."
  :group 'prolog-inferior
  :type 'sexp)

(defcustom prolog-consult-string
  '((eclipse "[%f].")
    (mercury nil)
    (sicstus (eval (if (prolog-atleast-version '(3 . 7))
                       "prolog:zap_file(%m,%b,consult,%l)."
                     "prolog:zap_file(%m,%b,consult).")))
    (swi "[%f].")
    (t "reconsult(%f)."))
  "*Alist of strings defining predicate for reconsulting.

Some parts of the string are replaced:
`%f' by the name of the consulted file (can be a temporary file)
`%b' by the file name of the buffer to consult
`%m' by the module name and name of the consulted file separated by colon
`%l' by the line offset into the file. This is 0 unless consulting a
     region of a buffer, in which case it is the number of lines before
     the region."
  :group 'prolog-inferior
  :type 'sexp)

(defcustom prolog-compile-string
  '((eclipse "[%f].")
    (mercury "mmake ")
    (sicstus (eval (if (prolog-atleast-version '(3 . 7))
                       "prolog:zap_file(%m,%b,compile,%l)."
                     "prolog:zap_file(%m,%b,compile).")))
    (swi "[%f].")
    (t "compile(%f)."))
  "*Alist of strings and lists defining predicate for recompilation.

Some parts of the string are replaced:
`%f' by the name of the compiled file (can be a temporary file)
`%b' by the file name of the buffer to compile
`%m' by the module name and name of the compiled file separated by colon
`%l' by the line offset into the file. This is 0 unless compiling a
     region of a buffer, in which case it is the number of lines before
     the region.

If `prolog-program-name' is non-nil, it is a string sent to a Prolog process.
If `prolog-program-name' is nil, it is an argument to the `compile' function."
  :group 'prolog-inferior
  :type 'sexp)

(defcustom prolog-eof-string "end_of_file.\n"
  "*Alist of strings that represent end of file for prolog.
nil means send actual operating system end of file."
  :group 'prolog-inferior
  :type 'sexp)

(defcustom prolog-prompt-regexp
  '((eclipse "^[a-zA-Z0-9()]* *\\?- \\|^\\[[a-zA-Z]* [0-9]*\\]:")
    (sicstus "| [ ?][- ] *")
    (swi "^\\(\\[[a-zA-Z]*\\] \\)?[1-9]?[0-9]*[ ]?\\?- \\|^| +")
    (t "^ *\\?-"))
  "*Alist of prompts of the prolog system command line."
  :group 'prolog-inferior
  :type 'sexp)

(defcustom prolog-continued-prompt-regexp
  '((sicstus "^\\(| +\\|     +\\)")
    (t "^|: +"))
  "*Alist of regexps matching the prompt when consulting `user'."
  :group 'prolog-inferior
  :type 'sexp)

(defcustom prolog-debug-on-string "debug.\n"
  "*Predicate for enabling debug mode."
  :group 'prolog-inferior
  :type 'string)

(defcustom prolog-debug-off-string "nodebug.\n"
  "*Predicate for disabling debug mode."
  :group 'prolog-inferior
  :type 'string)

(defcustom prolog-trace-on-string "trace.\n"
  "*Predicate for enabling tracing."
  :group 'prolog-inferior
  :type 'string)

(defcustom prolog-trace-off-string "notrace.\n"
  "*Predicate for disabling tracing."
  :group 'prolog-inferior
  :type 'string)

(defcustom prolog-zip-on-string "zip.\n"
  "*Predicate for enabling zip mode for SICStus."
  :group 'prolog-inferior
  :type 'string)

(defcustom prolog-zip-off-string "nozip.\n"
  "*Predicate for disabling zip mode for SICStus."
  :group 'prolog-inferior
  :type 'string)

(defcustom prolog-use-standard-consult-compile-method-flag t
  "*Non-nil means use the standard compilation method.
Otherwise the new compilation method will be used. This
utilises a special compilation buffer with the associated
features such as parsing of error messages and automatically
jumping to the source code responsible for the error.

Warning: the new method is so far only experimental and
does contain bugs. The recommended setting for the novice user
is non-nil for this variable."
  :group 'prolog-inferior
  :type 'boolean)


;; Miscellaneous

(defcustom prolog-use-prolog-tokenizer-flag t
  "*Non-nil means use the internal prolog tokenizer for indentation etc.
Otherwise use `parse-partial-sexp' which is faster but sometimes incorrect."
  :group 'prolog-other
  :type 'boolean)

(defcustom prolog-imenu-flag t
  "*Non-nil means add a clause index menu for all prolog files."
  :group 'prolog-other
  :type 'boolean)

(defcustom prolog-imenu-max-lines 3000
  "*The maximum number of lines of the file for imenu to be enabled.
Relevant only when `prolog-imenu-flag' is non-nil."
  :group 'prolog-other
  :type 'integer)

(defcustom prolog-info-predicate-index
  "(sicstus)Predicate Index"
  "*The info node for the SICStus predicate index."
  :group 'prolog-other
  :type 'string)

(defcustom prolog-underscore-wordchar-flag t
  "*Non-nil means underscore (_) is a word-constituent character."
  :group 'prolog-other
  :type 'boolean)

(defcustom prolog-use-sicstus-sd nil
  "*If non-nil, use the source level debugger of SICStus 3#7 and later."
  :group 'prolog-other
  :type 'boolean)


;;-------------------------------------------------------------------
;; Internal variables
;;-------------------------------------------------------------------

(defvar prolog-emacs 
  (if (string-match "XEmacs\\|Lucid" emacs-version)
      'xemacs
    'gnuemacs)
  "The variant of Emacs we're running.
Valid values are 'gnuemacs and 'xemacs.")

(defvar prolog-known-systems '(eclipse mercury sicstus swi))

(defvar prolog-temp-filename "")   ; Later set by `prolog-temporary-file'

(defvar prolog-mode-syntax-table nil)
(defvar prolog-mode-abbrev-table nil)
(defvar prolog-mode-map nil)
(defvar prolog-upper-case-string ""
  "A string containing all upper case characters.
Set by prolog-build-case-strings.")
(defvar prolog-lower-case-string ""
  "A string containing all lower case characters.
Set by prolog-build-case-strings.")
  
(defvar prolog-atom-char-regexp ""
  "Set by prolog-set-atom-regexps.")
;; "Regexp specifying characters which constitute atoms without quoting.")
(defconst prolog-atom-regexp ""
  "Set by prolog-set-atom-regexps.")

(defconst prolog-left-paren "[[({]" 
  "The characters used as left parentheses for the indentation code.")
(defconst prolog-right-paren "[])}]"
  "The characters used as right parentheses for the indentation code.")

(defconst prolog-quoted-atom-regexp
  "\\(^\\|[^0-9]\\)\\('\\([^\n']\\|\\\\'\\)*'\\)"
  "Regexp matching a quoted atom.")
(defconst prolog-string-regexp
  "\\(\"\\([^\n\"]\\|\\\\\"\\)*\"\\)"
  "Regexp matching a string.")
(defconst prolog-head-delimiter "\\(:-\\|\\+:\\|-:\\|\\+\\?\\|-\\?\\|-->\\)"
  "A regexp for matching on the end delimiter of a head (e.g. \":-\").")

(defvar prolog-compilation-buffer "*prolog-compilation*"
  "Name of the output buffer for Prolog compilation/consulting.")

(defvar prolog-keywords-i nil)
(defvar prolog-types-i nil)
(defvar prolog-mode-specificators-i nil)
(defvar prolog-determinism-specificators-i nil)
(defvar prolog-directives-i nil)
(defvar prolog-program-name-i nil)
(defvar prolog-program-switches-i nil)
(defvar prolog-consult-string-i nil)
(defvar prolog-compile-string-i nil)
(defvar prolog-eof-string-i nil)
(defvar prolog-prompt-regexp-i nil)
(defvar prolog-continued-prompt-regexp-i nil)
(defvar prolog-help-function-i nil)


;;-------------------------------------------------------------------
;; Prolog mode
;;-------------------------------------------------------------------

;; Example: (prolog-atleast-version '(3 . 6))
(defun prolog-atleast-version (version)
  "Return t if the version of the current prolog system is VERSION or later.
VERSION is of the format (Major . Minor)"
  ;; Version.major < major or
  ;; Version.major = major and Version.minor <= minor
  (let* ((thisversion (prolog-find-value-by-system prolog-system-version))
         (thismajor (car thisversion))
         (thisminor (cdr thisversion)))
    (or (< (car version) thismajor)
        (and (= (car version) thismajor)
             (<= (cdr version) thisminor)))
    ))

(if prolog-mode-syntax-table
    ()
  (let ((table (make-syntax-table)))
    (if prolog-underscore-wordchar-flag
        (modify-syntax-entry ?_ "w" table)
      (modify-syntax-entry ?_ "_" table))
    (modify-syntax-entry ?+ "." table)
    (modify-syntax-entry ?- "." table)
    (modify-syntax-entry ?= "." table)
    (modify-syntax-entry ?< "." table)
    (modify-syntax-entry ?> "." table)
    (modify-syntax-entry ?| "." table)
    (modify-syntax-entry ?\' "." table)

    (modify-syntax-entry ?% "<" table)
    (modify-syntax-entry ?\n ">" table)
    (if (eq prolog-emacs 'xemacs)
        (progn
          (modify-syntax-entry ?* ". 67" table)
          (modify-syntax-entry ?/ ". 58" table)
          )
      ;; Emacs wants to see this it seems:
      (modify-syntax-entry ?* ". 23b" table)
      (modify-syntax-entry ?/ ". 14" table)
    )

    (setq prolog-mode-syntax-table table)))

(define-abbrev-table 'prolog-mode-abbrev-table ())

(defun prolog-find-value-by-system (alist)
  "Get value from ALIST according to `prolog-system'."
  (if (listp alist)
      (let (result
            id)
        (while alist
          (setq id (car (car alist)))
          (if (or (eq id prolog-system)
                  (eq id t)
                  (and (listp id)
                       (eval id)))
              (progn
                (setq result (car (cdr (car alist))))
                (if (and (listp result)
                         (eq (car result) 'eval))
                    (setq result (eval (car (cdr result)))))
                (setq alist nil))
            (setq alist (cdr alist))))
        result)
    alist))

(defun prolog-mode-variables ()
  "Set some common variables to Prolog code specific values."
  (setq local-abbrev-table prolog-mode-abbrev-table)
  (make-local-variable 'paragraph-start)
  (setq paragraph-start (concat "[ \t]*$\\|" page-delimiter)) ;'%%..'
  (make-local-variable 'paragraph-separate)
  (setq paragraph-separate paragraph-start)
  (make-local-variable 'paragraph-ignore-fill-prefix)
  (setq paragraph-ignore-fill-prefix t)
  (make-local-variable 'adaptive-fill-mode)
  (setq adaptive-fill-mode nil)
  (make-local-variable 'indent-line-function)
  (setq indent-line-function 'prolog-indent-line)
  (make-local-variable 'comment-start)
  (setq comment-start "%")
  (make-local-variable 'comment-end)
  (setq comment-end "")
  (make-local-variable 'comment-start-skip)
  ;; This complex regexp makes sure that comments cannot start
  ;; inside quoted atoms or strings
  (setq comment-start-skip 
        (format "^\\(\\(%s\\|%s\\|[^\n\'\"%%]\\)*\\)\\(/\\*+ *\\|%%+ *\\)" 
                prolog-quoted-atom-regexp prolog-string-regexp))
  (make-local-variable 'comment-column)
  (make-local-variable 'comment-indent-function)
  (setq comment-indent-function 'prolog-comment-indent)
  (make-local-variable 'comment-indent-function)
  (setq comment-indent-function 'prolog-comment-indent)
  (make-local-variable 'parens-require-spaces)
  (setq parens-require-spaces nil)
  ;; Initialize Prolog system specific variables
  (let ((vars '(prolog-keywords prolog-types prolog-mode-specificators
                prolog-determinism-specificators prolog-directives
                prolog-program-name prolog-program-switches
                prolog-consult-string prolog-compile-string prolog-eof-string
                prolog-prompt-regexp prolog-continued-prompt-regexp
                prolog-help-function)))
    (while vars
      (set (intern (concat (symbol-name (car vars)) "-i"))
           (prolog-find-value-by-system (eval (car vars))))
      (setq vars (cdr vars))))
  (when (null prolog-program-name-i)
        (make-local-variable 'compile-command)
        (setq compile-command prolog-compile-string-i))
  (make-local-variable 'font-lock-defaults)
  (setq font-lock-defaults
        '(prolog-font-lock-keywords nil nil ((?_ . "w"))))
)

(defun prolog-mode-keybindings-common (map)
  "Define keybindings common to both Prolog modes in MAP."
  (define-key map "\C-c?" 'prolog-help-on-predicate)
  (define-key map "\C-c/" 'prolog-help-apropos)
  (define-key map "\C-c\C-d" 'prolog-debug-on)
  (define-key map "\C-c\C-t" 'prolog-trace-on)
  (if (and (eq prolog-system 'sicstus)
           (prolog-atleast-version '(3 . 7)))
      (define-key map "\C-c\C-z" 'prolog-zip-on))
  (define-key map "\C-c\r" 'run-prolog))

(defun prolog-mode-keybindings-edit (map)
  "Define keybindings for Prolog mode in MAP."
  (define-key map "\M-a" 'prolog-beginning-of-clause)
  (define-key map "\M-e" 'prolog-end-of-clause)
  (define-key map "\C-\M-a" 'prolog-beginning-of-predicate)
  (define-key map "\C-\M-e" 'prolog-end-of-predicate)
  (define-key map "\M-\C-c" 'prolog-mark-clause)
  (define-key map "\M-\C-h" 'prolog-mark-predicate)
  (define-key map "\M-\C-n" 'prolog-forward-list)
  (define-key map "\M-\C-p" 'prolog-backward-list)
  (define-key map "\C-c\C-n" 'prolog-insert-predicate-template)
  (define-key map "\C-c\C-s" 'prolog-insert-predspec)
  (define-key map "\M-\r" 'prolog-insert-next-clause)
  (define-key map "\C-c\C-va" 'prolog-variables-to-anonymous)
  (define-key map "\C-c\C-v\C-s" 'prolog-view-predspec)

  (define-key map "\177" 'prolog-electric-delete)
  (define-key map "." 'prolog-electric-dot)
  (define-key map "_" 'prolog-electric-underscore)
  (if prolog-electric-newline-flag 
      (define-key map "\r" 'newline-and-indent))

  ;; If we're running SICStus, then map C-c C-c e/d to enabling
  ;; and disabling of the source-level debugging facilities.
  ;(if (and (eq prolog-system 'sicstus)
  ;         (prolog-atleast-version '(3 . 7)))
  ;    (progn
  ;      (define-key map "\C-c\C-ce" 'prolog-enable-sicstus-sd)
  ;      (define-key map "\C-c\C-cd" 'prolog-disable-sicstus-sd)
  ;      ))

  (if prolog-old-sicstus-keys-flag
      (progn
        (define-key map "\C-c\C-c" 'prolog-consult-predicate)
        (define-key map "\C-cc" 'prolog-consult-region)
        (define-key map "\C-cC" 'prolog-consult-buffer)
        (define-key map "\C-c\C-k" 'prolog-compile-predicate)
        (define-key map "\C-ck" 'prolog-compile-region)
        (define-key map "\C-cK" 'prolog-compile-buffer))
    (define-key map "\C-c\C-p" 'prolog-consult-predicate)
    (define-key map "\C-c\C-r" 'prolog-consult-region)
    (define-key map "\C-c\C-b" 'prolog-consult-buffer)
    (define-key map "\C-c\C-f" 'prolog-consult-file)
    (define-key map "\C-c\C-cp" 'prolog-compile-predicate)
    (define-key map "\C-c\C-cr" 'prolog-compile-region)
    (define-key map "\C-c\C-cb" 'prolog-compile-buffer)
    (define-key map "\C-c\C-cf" 'prolog-compile-file)))

(defun prolog-mode-keybindings-inferior (map)
  "Define keybindings for inferior Prolog mode in MAP."
  ;; No inferior mode specific keybindings now.
  )

(if prolog-mode-map
    ()
  (setq prolog-mode-map (make-sparse-keymap))
  (prolog-mode-keybindings-common prolog-mode-map)
  (prolog-mode-keybindings-edit prolog-mode-map)
  ;; System dependent keymaps for system dependent menus
  (let ((systems prolog-known-systems))
    (while systems
      (set (intern (concat "prolog-mode-map-"
                           (symbol-name (car systems))))
           ;(cons 'keymap prolog-mode-map)
           prolog-mode-map
           )
      (setq systems (cdr systems))))
  )
  

(defvar prolog-mode-hook nil
  "List of functions to call after the prolog mode has initialised.")

;;;###autoload
(defun prolog-mode (&optional system)
  "Major mode for editing Prolog code.

Blank lines and `%%...' separate paragraphs.  `%'s starts a comment
line and comments can also be enclosed in /* ... */.

If an optional argument SYSTEM is non-nil, set up mode for the given system.

To find out what version of Prolog mode you are running, enter
`\\[prolog-mode-version]'.

Commands:
\\{prolog-mode-map}
Entry to this mode calls the value of `prolog-mode-hook'
if that value is non-nil."
  (interactive)
  (kill-all-local-variables)
  (if system (setq prolog-system system))
  (use-local-map
   (if prolog-system 
       ;; ### Looks like it works under XEmacs as well...
       ;; (and prolog-system
       ;;     (not (eq prolog-emacs 'xemacs)))
       (eval (intern (concat "prolog-mode-map-" (symbol-name prolog-system))))
     prolog-mode-map)
   )
  (setq major-mode 'prolog-mode)
  (setq mode-name (concat "Prolog"
                          (cond
                           ((eq prolog-system 'eclipse) "[ECLiPSe]")
                           ((eq prolog-system 'mercury) "[Mercury]")
                           ((eq prolog-system 'sicstus) "[SICStus]")
                           ((eq prolog-system 'swi) "[SWI]")
                           (t ""))))
  (set-syntax-table prolog-mode-syntax-table)
  (prolog-mode-variables)
  (prolog-build-case-strings)
  (prolog-set-atom-regexps)

  ;; imenu entry moved to the appropriate hook for consistency
  
  ;; Load SICStus debugger if suitable
  (if (and (eq prolog-system 'sicstus)
           (prolog-atleast-version '(3 . 7))
           prolog-use-sicstus-sd)
      (prolog-enable-sicstus-sd))
  
  (run-hooks 'prolog-mode-hook))

;;;###autoload
(defun mercury-mode ()
  "Major mode for editing Mercury programs.
Actually this is just customized `prolog-mode'."
  (interactive)
  (prolog-mode 'mercury))


;;-------------------------------------------------------------------
;; Inferior prolog mode
;;-------------------------------------------------------------------

(defvar prolog-inferior-mode-map nil)
(defvar prolog-inferior-mode-hook nil
  "List of functions to call after the inferior prolog mode has initialised.")

(defun prolog-inferior-mode ()
  "Major mode for interacting with an inferior Prolog process.

The following commands are available:
\\{prolog-inferior-mode-map}

Entry to this mode calls the value of `prolog-mode-hook' with no arguments,
if that value is non-nil.  Likewise with the value of `comint-mode-hook'.
`prolog-mode-hook' is called after `comint-mode-hook'.

You can send text to the inferior Prolog from other buffers
using the commands `send-region', `send-string' and \\[prolog-consult-region].

Commands:
Tab indents for Prolog; with argument, shifts rest
 of expression rigidly with the current line.
Paragraphs are separated only by blank lines and '%%'. '%'s start comments.

Return at end of buffer sends line as input.
Return not at end copies rest of line to end and sends it.
\\[comint-delchar-or-maybe-eof] sends end-of-file as input.
\\[comint-kill-input] and \\[backward-kill-word] are kill commands,
imitating normal Unix input editing.
\\[comint-interrupt-subjob] interrupts the shell or its current subjob if any.
\\[comint-stop-subjob] stops, likewise.
\\[comint-quit-subjob] sends quit signal, likewise.

To find out what version of Prolog mode you are running, enter
`\\[prolog-mode-version]'."
  (interactive)
  (cond ((not (eq major-mode 'prolog-inferior-mode))
         (kill-all-local-variables)
         (comint-mode)
         (setq comint-input-filter 'prolog-input-filter)
         (setq major-mode 'prolog-inferior-mode)
         (setq mode-name "Inferior Prolog")
         (setq mode-line-process '(": %s"))
         (prolog-mode-variables)
         (if prolog-inferior-mode-map
             ()
           (setq prolog-inferior-mode-map (copy-keymap comint-mode-map))
           (prolog-mode-keybindings-common prolog-inferior-mode-map)
           (prolog-mode-keybindings-inferior prolog-inferior-mode-map))
         (use-local-map prolog-inferior-mode-map)
         (setq comint-prompt-regexp prolog-prompt-regexp-i)
         (make-variable-buffer-local 'shell-dirstack-query)
         (setq shell-dirstack-query "pwd.")
         (run-hooks 'prolog-inferior-mode-hook))))

(defun prolog-input-filter (str)
  (cond ((string-match "\\`\\s *\\'" str) nil) ;whitespace
        ((not (eq major-mode 'prolog-inferior-mode)) t)
        ((= (length str) 1) nil)        ;one character
        ((string-match "\\`[rf] *[0-9]*\\'" str) nil) ;r(edo) or f(ail)
        (t t)))

;;;###autoload
(defun run-prolog (arg)
  "Run an inferior Prolog process, input and output via buffer *prolog*.
With prefix argument ARG, restart the Prolog process if running before."
  (interactive "P")
  (if (and arg (get-process "prolog"))
      (progn
        (process-send-string "prolog" "halt.\n")
        (while (get-process "prolog") (sit-for 0.1))))
  (let ((buff (buffer-name)))
    (if (not (string= buff "*prolog*"))
        (prolog-goto-prolog-process-buffer))
    ;; Load SICStus debugger if suitable
    (if (and (eq prolog-system 'sicstus)
             (prolog-atleast-version '(3 . 7))
             prolog-use-sicstus-sd)
        (prolog-enable-sicstus-sd))
    (prolog-mode-variables)
    (prolog-ensure-process)
    ))

(defun prolog-ensure-process (&optional wait)
  "If Prolog process is not running, run it.
If the optional argument WAIT is non-nil, wait for Prolog prompt specified by
the variable `prolog-prompt-regexp'."
  (if (null prolog-program-name-i)
      (error "This Prolog system has defined no interpreter."))
  (if (comint-check-proc "*prolog*")
      ()
    (apply 'make-comint "prolog" prolog-program-name-i nil
           prolog-program-switches-i)
    (save-excursion
      (set-buffer "*prolog*")
      (prolog-inferior-mode)
      (if wait
          (progn
            (goto-char (point-max))
            (while
                (save-excursion
                  (not
                   (re-search-backward
                    (concat "\\(" prolog-prompt-regexp-i "\\)" "\\=")
                    nil t)))
              (sit-for 0.1)))))))

(defun prolog-process-insert-string (process string)
  "Insert STRING into inferior Prolog buffer running PROCESS."
  ;; Copied from elisp manual, greek to me
  (let ((buf (current-buffer)))
    (unwind-protect
        (let (moving)
          (set-buffer (process-buffer process))
          (setq moving (= (point) (process-mark process)))
          (save-excursion
            ;; Insert the text, moving the process-marker.
            (goto-char (process-mark process))
            (insert string)
            (set-marker (process-mark process) (point)))
          (if moving (goto-char (process-mark process))))
      (set-buffer buf))))


;;------------------------------------------------------------
;; Old consulting and compiling functions
;;------------------------------------------------------------

(defun prolog-old-process-region (compilep start end)
  "Process the region limited by START and END positions.
If COMPILEP is non-nil then use compilation, otherwise consulting."
   (prolog-ensure-process)
   (let ((tmpfile prolog-temp-filename)
         ;(process (get-process "prolog"))
         (first-line (1+ (count-lines 
                          (point-min) 
                          (save-excursion
                            (goto-char start)
                            (point))))))
     (write-region start end tmpfile)
     (process-send-string
      "prolog" (prolog-build-prolog-command
                compilep tmpfile (prolog-bsts buffer-file-name)
                first-line))
     (prolog-goto-prolog-process-buffer)))

(defun prolog-old-process-predicate (compilep)
  "Process the predicate around point.
If COMPILEP is non-nil then use compilation, otherwise consulting."
  (prolog-old-process-region
   compilep (prolog-pred-start) (prolog-pred-end)))

(defun prolog-old-process-buffer (compilep)
  "Process the entire buffer.
If COMPILEP is non-nil then use compilation, otherwise consulting."
  (prolog-old-process-region compilep (point-min) (point-max)))

(defun prolog-old-process-file (compilep)
  "Process the file of the current buffer.
If COMPILEP is non-nil then use compilation, otherwise consulting."
  (save-some-buffers)
  (prolog-ensure-process)
  (let ((filename (prolog-bsts buffer-file-name)))
    (process-send-string
     "prolog" (prolog-build-prolog-command 
               compilep filename filename))
    (prolog-goto-prolog-process-buffer)))


;;------------------------------------------------------------
;; Consulting and compiling
;;------------------------------------------------------------

;;; Interactive interface functions, used by both the standard
;;; and the experimental consultation and compilation functions
(defun prolog-consult-file ()
  "Consult file of current buffer."
  (interactive)
  (if prolog-use-standard-consult-compile-method-flag
      (prolog-old-process-file nil)
    (prolog-consult-compile-file nil)))

(defun prolog-consult-buffer ()
  "Consult buffer."
  (interactive)
  (if prolog-use-standard-consult-compile-method-flag
      (prolog-old-process-buffer nil)
    (prolog-consult-compile-buffer nil)))

(defun prolog-consult-region (beg end)
  "Consult region between BEG and END."
  (interactive "r")
  (if prolog-use-standard-consult-compile-method-flag
      (prolog-old-process-region nil beg end)
    (prolog-consult-compile-region nil beg end)))

(defun prolog-consult-predicate ()
  "Consult the predicate around current point."
  (interactive)
  (if prolog-use-standard-consult-compile-method-flag
      (prolog-old-process-predicate nil)
    (prolog-consult-compile-predicate nil)))

(defun prolog-compile-file ()
  "Compile file of current buffer."
  (interactive)
  (if prolog-use-standard-consult-compile-method-flag
      (prolog-old-process-file t)
    (prolog-consult-compile-file t)))

(defun prolog-compile-buffer ()
  "Compile buffer."
  (interactive)
  (if prolog-use-standard-consult-compile-method-flag
      (prolog-old-process-buffer t)
    (prolog-consult-compile-buffer t)))

(defun prolog-compile-region (beg end)
  "Compile region between BEG and END."
  (interactive "r")
  (if prolog-use-standard-consult-compile-method-flag
      (prolog-old-process-region t beg end)
    (prolog-consult-compile-region t beg end)))

(defun prolog-compile-predicate ()
  "Compile the predicate around current point."
  (interactive)
  (if prolog-use-standard-consult-compile-method-flag
      (prolog-old-process-predicate t)
    (prolog-consult-compile-predicate t)))

(defun prolog-buffer-module ()
  "Select Prolog module name appropriate for current buffer.
Bases decision on buffer contents (-*- line)."
  ;; Look for -*- ... module: MODULENAME; ... -*-
  (let (beg end)
    (save-excursion
      (goto-char (point-min))
      (skip-chars-forward " \t")
      (and (search-forward "-*-" (save-excursion (end-of-line) (point)) t)
           (progn
             (skip-chars-forward " \t")
             (setq beg (point))
             (search-forward "-*-" (save-excursion (end-of-line) (point)) t))
           (progn
             (forward-char -3)
             (skip-chars-backward " \t")
             (setq end (point))
             (goto-char beg)
             (and (let ((case-fold-search t))
                    (search-forward "module:" end t))
                  (progn
                    (skip-chars-forward " \t")
                    (setq beg (point))
                    (if (search-forward ";" end t)
                        (forward-char -1)
                      (goto-char end))
                    (skip-chars-backward " \t")
                    (buffer-substring beg (point)))))))))

(defun prolog-build-prolog-command (compilep file buffername 
                                    &optional first-line)
  "Make Prolog command for FILE compilation/consulting.
If COMPILEP is non-nil, consider compilation, otherwise consulting."
  (let* ((compile-string
          (if compilep prolog-compile-string-i prolog-consult-string-i))
         (module (prolog-buffer-module))
         (file-name (concat "'" file "'"))
         (module-name (if module (concat "'" module "'")))
         (module-file (if module
                          (concat module-name ":" file-name)
                        file-name))
         strbeg strend
         (lineoffset (if first-line
                         (- first-line 1)
                       0)))

    ;; Assure that there is a buffer name
    (if (not buffername)
        (error "The buffer is not saved"))

    (if (not (string-match "^'.*'$" buffername)) ; Add quotes
        (setq buffername (concat "'" buffername "'")))
    (while (string-match "%m" compile-string)
      (setq strbeg (substring compile-string 0 (match-beginning 0)))
      (setq strend (substring compile-string (match-end 0)))
      (setq compile-string (concat strbeg module-file strend)))
    (while (string-match "%f" compile-string)
      (setq strbeg (substring compile-string 0 (match-beginning 0)))
      (setq strend (substring compile-string (match-end 0)))
      (setq compile-string (concat strbeg file-name strend)))
    (while (string-match "%b" compile-string)
      (setq strbeg (substring compile-string 0 (match-beginning 0)))
      (setq strend (substring compile-string (match-end 0)))
      (setq compile-string (concat strbeg buffername strend)))
    (while (string-match "%l" compile-string)
      (setq strbeg (substring compile-string 0 (match-beginning 0)))
      (setq strend (substring compile-string (match-end 0)))
      (setq compile-string (concat strbeg (format "%d" lineoffset) strend)))
    (concat compile-string "\n")))

;;; The rest of this page is experimental code!

;; Global variables for process filter function
(defvar prolog-process-flag nil
  "Non-nil means that a prolog task (i.e. a consultation or compilation job) 
is running.")
(defvar prolog-consult-compile-output ""
  "Hold the unprocessed output from the current prolog task.")
(defvar prolog-consult-compile-first-line 1
  "The number of the first line of the file to consult/compile.
Used for temporary files.")
(defvar prolog-consult-compile-file nil
  "The file to compile/consult (can be a temporary file).")
(defvar prolog-consult-compile-real-file nil
  "The file name of the buffer to compile/consult.")

(defun prolog-consult-compile (compilep file &optional first-line)
  "Consult/compile FILE.
If COMPILEP is non-nil, perform compilation, otherwise perform CONSULTING.
COMMAND is a string described by the variables `prolog-consult-string'
and `prolog-compile-string'.
Optional argument FIRST-LINE is the number of the first line in the compiled
region.

This function must be called from the source code buffer."
  (if prolog-process-flag
      (error "Another Prolog task is running."))
  (prolog-ensure-process t)
  (let* ((buffer (get-buffer-create prolog-compilation-buffer))
         (real-file buffer-file-name)
         (command-string (prolog-build-prolog-command compilep file 
                                                      real-file first-line))
         (process (get-process "prolog"))
         (old-filter (process-filter process)))
    (save-excursion
      (set-buffer buffer)
      (delete-region (point-min) (point-max))
      (compilation-mode)
      ;; Setting up font-locking for this buffer
      (make-local-variable 'font-lock-defaults)
      (setq font-lock-defaults 
            '(prolog-font-lock-keywords nil nil ((?_ . "w"))))
      (if (eq prolog-system 'sicstus)
          (progn
            (make-local-variable 'compilation-parse-errors-function)
            (setq compilation-parse-errors-function
                  'prolog-parse-sicstus-compilation-errors)))
      (insert command-string "\n"))
    (save-selected-window
      (pop-to-buffer buffer))
    (setq prolog-process-flag t
          prolog-consult-compile-output ""
          prolog-consult-compile-first-line (if first-line (1- first-line) 0)
          prolog-consult-compile-file file
          prolog-consult-compile-real-file (if (string= 
                                                file buffer-file-name)
                                               nil
                                             real-file))
    (save-excursion
      (set-buffer buffer)
      (goto-char (point-max))
      (set-process-filter process 'prolog-consult-compile-filter)
      (process-send-string
       "prolog"
       command-string)
      ;; (prolog-build-prolog-command compilep file real-file first-line))
      (while (and prolog-process-flag
                  (accept-process-output process 10)) ; 10 secs is ok?
        (sit-for 0.1)
        (if (not (get-process "prolog"))
            (setq prolog-process-flag nil)))
      (insert (if compilep
                  "\nCompilation finished.\n"
                "\nConsulted.\n"))
      (set-process-filter process old-filter))))

(defun prolog-parse-sicstus-compilation-errors (limit)
  "Parse the prolog compilation buffer for errors.
Argument LIMIT is a buffer position limiting searching.
For use with the `compilation-parse-errors-function' variable."
  (setq compilation-error-list nil)
  (message "Parsing SICStus error messages...")
  (let (filepath dir file errorline)
    (while 
        (re-search-backward
         "{\\([a-zA-Z ]* ERROR\\|Warning\\):.* in line[s ]*\\([0-9]+\\)"
         limit t)
      (setq errorline (string-to-number (match-string 2)))
      (save-excursion
        (re-search-backward
         "{\\(consulting\\|compiling\\|processing\\) \\(.*\\)\\.\\.\\.}"
         limit t)
        (setq filepath (match-string 2)))

      ;; ###### Does this work with SICStus under Windows (i.e. backslahes and stuff?)
      (if (string-match "\\(.*/\\)\\([^/]*\\)$" filepath)
          (progn
            (setq dir (match-string 1 filepath))
            (setq file (match-string 2 filepath))))

      (setq compilation-error-list
            (cons
             (cons (save-excursion
                     (beginning-of-line)
                     (point-marker))
                   (list (list file dir) errorline))
             compilation-error-list)
            ))
    ))

(defun prolog-consult-compile-filter (process output)
  "Filter function for Prolog compilation PROCESS.
Argument OUTPUT is a name of the output file."
  ;;(message "start")
  (setq prolog-consult-compile-output
        (concat prolog-consult-compile-output output))
  ;;(message "pccf1: %s" prolog-consult-compile-output)
  ;; Iterate through the lines of prolog-consult-compile-output
  (let (outputtype)
    (while (and prolog-process-flag
                (or
                 ;; Trace question
                 (progn 
                   (setq outputtype 'trace)
                   (and (eq prolog-system 'sicstus)
                        (string-match
                         "^[ \t]*[0-9]+[ \t]*[0-9]+[ \t]*Call:.*? "
                         prolog-consult-compile-output)))
                 
                 ;; Match anything
                 (progn 
                   (setq outputtype 'normal)
                   (string-match "^.*\n" prolog-consult-compile-output))
                   ))
      ;;(message "outputtype: %s" outputtype)

      (setq output (match-string 0 prolog-consult-compile-output))
      ;; remove the text in output from prolog-consult-compile-output
      (setq prolog-consult-compile-output
            (substring prolog-consult-compile-output (length output)))
      ;;(message "pccf2: %s" prolog-consult-compile-output)
      
      ;; If temporary files were used, then we change the error
      ;; messages to point to the original source file.
      (cond

       ;; If the prolog process was in trace mode then it requires
       ;; user input
       ((and (eq prolog-system 'sicstus) 
             (eq outputtype 'trace))
        (let (input)
          (setq input (concat (read-string output) "\n"))
          (process-send-string "prolog" input)
          (setq output (concat output input))))

       ((eq prolog-system 'sicstus)
        (if (and prolog-consult-compile-real-file
                 (string-match
                  "\\({.*:.* in line[s ]*\\)\\([0-9]+\\)-\\([0-9]+\\)" output))
            (setq output (replace-match
                          ;; Adds a {processing ...} line so that 
                          ;; `prolog-parse-sicstus-compilation-errors'
                          ;; finds the real file instead of the temporary one.
                          ;; Also fixes the line numbers.
                          (format "Added by Emacs: {processing %s...}\n%s%d-%d"
                                  prolog-consult-compile-real-file
                                  (match-string 1 output)
                                  (+ prolog-consult-compile-first-line
                                     (string-to-number
                                      (match-string 2 output)))
                                  (+ prolog-consult-compile-first-line
                                     (string-to-number
                                      (match-string 3 output))))
                          t t output)))
        )
       
       ((eq prolog-system 'swi)
        (if (and prolog-consult-compile-real-file
                 (string-match (format
                                "%s\\([ \t]*:[ \t]*\\)\\([0-9]+\\)"
                                prolog-consult-compile-file)
                               output))
            (setq output (replace-match
                          ;; Real filename + text + fixed linenum
                          (format "%s%s%d"
                                  prolog-consult-compile-real-file
                                  (match-string 1 output)
                                  (+ prolog-consult-compile-first-line
                                     (string-to-number
                                      (match-string 2 output))))
                          t t output)))
        )
       
       (t ())
       )
      ;; Write the output in the *prolog-compilation* buffer
      (insert output)))

  ;; If the prompt is visible, then the task is finished
  (if (string-match prolog-prompt-regexp-i prolog-consult-compile-output)
      (setq prolog-process-flag nil)))

(defun prolog-consult-compile-file (compilep)
  "Consult/compile file of current buffer.
If COMPILEP is non-nil, compile, otherwise consult."
  (let ((file buffer-file-name))
    (if file
        (progn
          (save-some-buffers)
          (prolog-consult-compile compilep file))
      (prolog-consult-compile-region compilep (point-min) (point-max)))))

(defun prolog-consult-compile-buffer (compilep)
  "Consult/compile current buffer.
If COMPILEP is non-nil, compile, otherwise consult."
  (prolog-consult-compile-region compilep (point-min) (point-max)))

(defun prolog-consult-compile-region (compilep beg end)
  "Consult/compile region between BEG and END.
If COMPILEP is non-nil, compile, otherwise consult."
  (let ((file prolog-temp-filename)
        (lines (count-lines 1 beg)))
    (write-region beg end file nil 'no-message)
    (write-region "\n" nil file t 'no-message)
    (prolog-consult-compile compilep file
                            (if (looking-at "^") (1+ lines) lines))
    (delete-file file)))

(defun prolog-consult-compile-predicate (compilep)
  "Consult/compile the predicate around current point.
If COMPILEP is non-nil, compile, otherwise consult."
  (prolog-consult-compile-region
   compilep (prolog-pred-start) (prolog-pred-end)))


;;-------------------------------------------------------------------
;; Font-lock stuff
;;-------------------------------------------------------------------

;; Auxilliary functions
(defun prolog-make-keywords-regexp (keywords &optional protect)
  "Create regexp from the list of strings KEYWORDS.
If PROTECT is non-nil, surround the result regexp by word breaks."
  (let ((regexp
         (if (fboundp 'regexp-opt)
             ;; Emacs 20
             ;; Avoid compile warnings under earlier versions by using eval
             (eval '(regexp-opt keywords))
           ;; Older Emacsen
           (concat (mapconcat 'regexp-quote keywords "\\|")))
         ))
    (if protect
        (concat "\\<\\(" regexp "\\)\\>")
      regexp)))

(defun prolog-font-lock-object-matcher (bound)
  "Find SICStus objects method name for font lock.
Argument BOUND is a buffer position limiting searching."
  (let (point
         (case-fold-search nil))
    (while (and (not point)
                (re-search-forward "\\(::[ \t\n]*{\\|&\\)[ \t]*"
                                   bound t))
      (while (or (re-search-forward "\\=\n[ \t]*" bound t)
                  (re-search-forward "\\=%.*" bound t)
                  (and (re-search-forward "\\=/\\*" bound t)
                       (re-search-forward "\\*/[ \t]*" bound t))))
      (setq point (re-search-forward
                   (format "\\=\\(%s\\)" prolog-atom-regexp)
                   bound t)))
    point))

;; Set everything up
(defun prolog-font-lock-keywords ()
  "Set up font lock keywords for the current Prolog system."
  (when window-system
    (require 'font-lock)
    
    ;; Define Prolog faces
    (defface prolog-redo-face
      '((((class grayscale)) (:italic t))
        (((class color)) (:foreground "darkorchid"))
        (t (:italic t)))
      "Prolog mode face for highlighting redo trace lines."
      :group 'prolog-faces)
    (defface prolog-exit-face
      '((((class grayscale)) (:underline t))
        (((class color) (background dark)) (:foreground "green"))
        (((class color) (background light)) (:foreground "ForestGreen"))
        (t (:underline t)))
      "Prolog mode face for highlighting exit trace lines."
      :group 'prolog-faces)
    (defface prolog-exception-face
      '((((class grayscale)) (:bold t :italic t :underline t))
        (((class color)) (:bold t :foreground "black" :background "Khaki"))
        (t (:bold t :italic t :underline t)))
      "Prolog mode face for highlighting exception trace lines."
      :group 'prolog-faces)
    (defvar prolog-warning-face 'font-lock-warning-face
      "Face name to use for compiler warnings.")
    (defvar prolog-builtin-face 'font-lock-builtin-face
      "Face name to use for built in predicates.")
    (defvar prolog-redo-face 'prolog-redo-face
      "Face name to use for redo trace lines.")
    (defvar prolog-exit-face 'prolog-exit-face
      "Face name to use for exit trace lines.")
    (defvar prolog-exception-face 'prolog-exception-face
      "Face name to use for exception trace lines.")
    
    ;; Font Lock Patterns
    (let (
          ;; "Native" Prolog patterns
          (head-predicates
           (list (format "^%s" prolog-atom-regexp)
                 0 font-lock-function-name-face))
          (variables
           '("\\<\\([_A-Z][a-zA-Z0-9_]*\\)"
             1 font-lock-variable-name-face))
          (important-elements
           (list (if (eq prolog-system 'mercury)
                     "[][}{;|]\\|\\\\[+=]\\|<?=>?"
                   "[][}{!;|]\\|\\*->")
                 0 'font-lock-keyword-face))
          (important-elements-1
           '("[^-*]\\(->\\)" 1 font-lock-keyword-face))
          (predspecs                        ; module:predicate/cardinality
           (list (format "\\<\\(%s:\\|\\)%s/[0-9]+"
                         prolog-atom-regexp prolog-atom-regexp)
                 0 font-lock-function-name-face 'prepend))
          (keywords                        ; directives (queries)
           (list
            (if (eq prolog-system 'mercury)
                (concat
                 "\\<\\("
                 (prolog-make-keywords-regexp prolog-keywords-i)
                 "\\|"
                 (prolog-make-keywords-regexp
                  prolog-determinism-specificators-i)
                 "\\)\\>")
              (concat
               "^[?:]- *\\("
               (prolog-make-keywords-regexp prolog-keywords-i)
               "\\)\\>"))
              1 prolog-builtin-face))
          (quoted_atom (list prolog-quoted-atom-regexp
                             2 'font-lock-string-face 'append))
          (string (list prolog-string-regexp
                        1 'font-lock-string-face 'append))
          ;; SICStus specific patterns
          (sicstus-object-methods
           (if (eq prolog-system 'sicstus)
               '(prolog-font-lock-object-matcher
                 1 font-lock-function-name-face)))
          ;; Mercury specific patterns
          (types
           (if (eq prolog-system 'mercury)
               (list
                (prolog-make-keywords-regexp prolog-types-i t)
                0 'font-lock-type-face)))
          (modes
           (if (eq prolog-system 'mercury)
               (list
                (prolog-make-keywords-regexp prolog-mode-specificators-i t)
                0 'font-lock-reference-face)))
          (directives
           (if (eq prolog-system 'mercury)
               (list
                (prolog-make-keywords-regexp prolog-directives-i t)
                0 'prolog-warning-face)))
          ;; Inferior mode specific patterns
          (prompt
           (list prolog-prompt-regexp-i 0 'font-lock-keyword-face))
          (trace-exit
           (cond
            ((eq prolog-system 'sicstus)
             '("[ \t]*[0-9]+[ \t]+[0-9]+[ \t]*\\(Exit\\):"
               1 prolog-exit-face))
            ((eq prolog-system 'swi)
             '("[ \t]*\\(Exit\\):[ \t]*([ \t0-9]*)" 1 prolog-exit-face))
            (t nil)))
          (trace-fail
           (cond
            ((eq prolog-system 'sicstus)
             '("[ \t]*[0-9]+[ \t]+[0-9]+[ \t]*\\(Fail\\):"
               1 prolog-warning-face))
            ((eq prolog-system 'swi)
             '("[ \t]*\\(Fail\\):[ \t]*([ \t0-9]*)" 1 prolog-warning-face))
            (t nil)))
          (trace-redo
           (cond
            ((eq prolog-system 'sicstus)
             '("[ \t]*[0-9]+[ \t]+[0-9]+[ \t]*\\(Redo\\):"
               1 prolog-redo-face))
            ((eq prolog-system 'swi)
             '("[ \t]*\\(Redo\\):[ \t]*([ \t0-9]*)" 1 prolog-redo-face))
            (t nil)))
          (trace-call
           (cond
            ((eq prolog-system 'sicstus)
             '("[ \t]*[0-9]+[ \t]+[0-9]+[ \t]*\\(Call\\):"
               1 font-lock-function-name-face))
            ((eq prolog-system 'swi)
             '("[ \t]*\\(Call\\):[ \t]*([ \t0-9]*)"
               1 font-lock-function-name-face))
            (t nil)))
          (trace-exception
           (cond
            ((eq prolog-system 'sicstus)
             '("[ \t]*[0-9]+[ \t]+[0-9]+[ \t]*\\(Exception\\):"
               1 prolog-exception-face))
            ((eq prolog-system 'swi)
             '("[ \t]*\\(Exception\\):[ \t]*([ \t0-9]*)"
               1 prolog-exception-face))
            (t nil)))
          (error-message-identifier
           (cond
            ((eq prolog-system 'sicstus)
             '("{\\([A-Z]* ?ERROR:\\)" 1 prolog-exception-face prepend))
            ((eq prolog-system 'swi)
             '("^[[]\\(WARNING:\\)" 1 prolog-builtin-face prepend))
            (t nil)))
          (error-whole-messages
           (cond
            ((eq prolog-system 'sicstus)
             '("{\\([A-Z]* ?ERROR:.*\\)}[ \t]*$"
               1 font-lock-comment-face append))
            ((eq prolog-system 'swi)
             '("^[[]WARNING:[^]]*[]]$" 0 font-lock-comment-face append))
            (t nil)))
          (error-warning-messages
           ;; Mostly errors that SICStus asks the user about how to solve,
           ;; such as "NAME CLASH:" for example.
           (cond
            ((eq prolog-system 'sicstus)
             '("^[A-Z ]*[A-Z]+:" 0 prolog-warning-face))
            (t nil)))
          (warning-messages
           (cond
            ((eq prolog-system 'sicstus)
             '("\\({ ?\\(Warning\\|WARNING\\) ?:.*}\\)[ \t]*$" 
               2 prolog-warning-face prepend))
            (t nil))))

      ;; Make font lock list
      (delq
       nil
       (cond
        ((eq major-mode 'prolog-mode)
         (list
          head-predicates
          quoted_atom
          string
          variables
          important-elements
          important-elements-1
          predspecs
          keywords
          sicstus-object-methods
          types
          modes
          directives))
        ((eq major-mode 'prolog-inferior-mode)
         (list
         prompt
         error-message-identifier
         error-whole-messages
         error-warning-messages
         warning-messages
         predspecs
         trace-exit
         trace-fail
         trace-redo
         trace-call
         trace-exception))
        ((eq major-mode 'compilation-mode)
         (list
         error-message-identifier
         error-whole-messages
         error-warning-messages
         warning-messages
         predspecs))))
      )))


;;-------------------------------------------------------------------
;; Indentation stuff
;;-------------------------------------------------------------------

;; NB: This function *MUST* have this optional argument since XEmacs
;; assumes it. This does not mean we have to use it...
(defun prolog-indent-line (&optional whole-exp)
  "Indent current line as Prolog code.
With argument, indent any additional lines of the same clause
rigidly along with this one (not yet)."
  (interactive "p")
  (let ((indent (prolog-indent-level))
        (pos (- (point-max) (point))) beg)
    (beginning-of-line)
    (setq beg (point))
    (skip-chars-forward " \t")
    (if (zerop (- indent (current-column)))
        nil
      (delete-region beg (point))
      (indent-to indent))
    (if (> (- (point-max) pos) (point))
        (goto-char (- (point-max) pos)))
    
    ;; Align comments
    (if prolog-align-comments-flag
        (save-excursion
          (prolog-goto-comment-column t)))

    ;; Insert spaces if needed
    (if prolog-electric-tab-flag
        (prolog-insert-spaces-after-paren))
    ))

(defun prolog-comment-indent ()
  "Compute prolog comment indentation."
  (cond ((looking-at "%%%") (prolog-indentation-level-of-line))
        ((looking-at "%%") (prolog-indent-level))
        (t
         (save-excursion
           (skip-chars-backward " \t")
           ;; Insert one space at least, except at left margin.
           (max (+ (current-column) (if (bolp) 0 1))
                comment-column)))
        ))

(defun prolog-indent-level ()
  "Compute prolog indentation level."
  (save-excursion
    (beginning-of-line)
    (let ((totbal (prolog-region-paren-balance
                   (prolog-clause-start t) (point)))
          (oldpoint (point)))
      (skip-chars-forward " \t")
      (cond
       ((looking-at "%%%") (prolog-indentation-level-of-line))
                                        ;Large comment starts
       ((looking-at "%[^%]") comment-column) ;Small comment starts
       ((bobp) 0)                        ;Beginning of buffer

       ;; If we found '}' then we must check if it's the
       ;; end of an object declaration or something else.
       ((and (looking-at "}") 
             (save-excursion
               (forward-char 1)
               ;; Goto to matching {
               (if prolog-use-prolog-tokenizer-flag
                   (prolog-backward-list)
                 (backward-list))
               (skip-chars-backward " \t")
               (backward-char 2)
               (looking-at "::")))
        ;; It was an object
        (if prolog-object-end-to-0-flag
            0
          prolog-indent-width)) 

       ;;End of /* */ comment
       ((looking-at "\\*/")                  
        (save-excursion
          (prolog-find-start-of-mline-comment)
          (skip-chars-backward " \t")
          (- (current-column) 2)))

       ;; Here we check if the current line is within a /* */ pair
       ((and (looking-at "[^%/]")
             (eq (prolog-in-string-or-comment) 'cmt)) 
        (if prolog-indent-mline-comments-flag
            (prolog-find-start-of-mline-comment)
          ;; Same as before
          (prolog-indentation-level-of-line)))

       (t
        (let ((empty t) ind linebal)
          ;; See previous indentation
          (while empty
            (forward-line -1)
            (beginning-of-line)
            (if (= (point) (point-min))
                (setq empty nil)
              (skip-chars-forward " \t")
              (if (not (or (prolog-in-string-or-comment)
                           (looking-at "%") 
                           (looking-at "\n")))
                  (setq empty nil))))

          ;; Store this line's indentation
          (if (= (point) (point-min))
              (setq ind 0)                ;Beginning of buffer
            (setq ind (current-column))) ;Beginning of clause

          ;; Compute the balance of the line
          (setq linebal (prolog-paren-balance))
          ;;(message "bal of previous line %d totbal %d" linebal totbal)
          (if (< linebal 0)
              (progn
                ;; Add 'indent-level' mode to find-unmatched-paren instead?
                (end-of-line)
                (setq ind (prolog-find-indent-of-matching-paren))))

          ;;(message "ind %d" ind)
          (beginning-of-line)

          ;; Check if the line ends with ":-", ".", ":: {", "}" (might be
          ;; unnecessary), "&" or ")" (The last four concerns SICStus objects)
          (cond
           ;; If the last char of the line is a '&' then set the indent level
           ;; to prolog-indent-width (used in SICStus objects)
           ((and (eq prolog-system 'sicstus) 
                 (looking-at ".+&[ \t]*\\(%.*\\|\\)$"))
            (setq ind prolog-indent-width))

           ;; Increase indentation if the previous line was the head of a rule
           ;; and does not contain a '.'
           ((and (looking-at (format ".*%s[^\\.]*[ \t]*\\(%%.*\\|\\)$" 
                                     prolog-head-delimiter))
                 ;; We must check that the match is at a paren balance of 0.
                 (save-excursion
                   (let ((p (point)))
                     (re-search-forward prolog-head-delimiter)
                     (>= 0 (prolog-region-paren-balance p (point))))))
            (let (headindent)
              (if (< (prolog-paren-balance) 0)
                  (save-excursion
                    (end-of-line)
                    (setq headindent (prolog-find-indent-of-matching-paren)))
                (setq headindent (prolog-indentation-level-of-line)))
              (setq ind (+ headindent prolog-indent-width))))

           ;; The previous line was the head of an object
           ((looking-at ".+ *::.*{[ \t]*$")
            (setq ind prolog-indent-width))

           ;; If a '.' is found at the end of the previous line, then
           ;; decrease the indentation. (The \\(%.*\\|\\) part of the
           ;; regexp is for comments at the end of the line)
           ((and (looking-at "^.+\\.[ \t]*\\(%.*\\|\\)$") 
                 ;; Make sure that the '.' found is not in a comment or string
                 (save-excursion
                   (end-of-line)
                   (re-search-backward "\\.[ \t]*\\(%.*\\|\\)$" (point-min))
                   ;; Guard against the real '.' being followed by a
                   ;; commented '.'.
                   (if (eq (prolog-in-string-or-comment) 'cmt)  ;; commented out '.'
                       (let ((here (save-excursion
                                     (beginning-of-line)
                                     (point))))
                         (end-of-line)
                         (re-search-backward "\\.[ \t]*%.*$" here t))
                     (not (prolog-in-string-or-comment))
                     )
                   ))
            (setq ind 0))

           ;; If a '.' is found at the end of the previous line, then
           ;; decrease the indentation. (The /\\*.*\\*/ part of the
           ;; regexp is for C-like comments at the end of the
           ;; line--can we merge with the case above?).
           ((and (looking-at "^.+\\.[ \t]*\\(/\\*.*\\|\\)$") 
                 ;; Make sure that the '.' found is not in a comment or string
                 (save-excursion
                   (end-of-line)
                   (re-search-backward "\\.[ \t]*\\(/\\*.*\\|\\)$" (point-min))
                   ;; Guard against the real '.' being followed by a
                   ;; commented '.'.
                   (if (eq (prolog-in-string-or-comment) 'cmt)  ;; commented out '.'
                       (let ((here (save-excursion
                                     (beginning-of-line)
                                     (point))))
                         (end-of-line)
                         (re-search-backward "\\.[ \t]*/\\*.*$" here t))
                     (not (prolog-in-string-or-comment))
                     )
                   ))
            (setq ind 0))

           )

          ;; If the last non comment char is a ',' or left paren or a left-
          ;; indent-regexp then indent to open parenthesis level
          (if (and
               (> totbal 0)
               ;; SICStus objects have special syntax rules if point is
               ;; not inside additional parens (objects are defined
               ;; within {...})
               (not (and (eq prolog-system 'sicstus)
                         (= totbal 1)
                         (prolog-in-object))))
              (if (looking-at
                   (format "\\(%s\\|%s\\|0'.\\|[0-9]+'[0-9a-zA-Z]+\\|[^\n\'\"%%]\\)*\\(,\\|%s\\|%s\\)\[ \t]*\\(%%.*\\|\\)$" 
                           prolog-quoted-atom-regexp prolog-string-regexp
                           prolog-left-paren prolog-left-indent-regexp))
                  (progn
                    (goto-char oldpoint)
                    (setq ind (prolog-find-unmatched-paren 'termdependent)))
                (goto-char oldpoint)
                (setq ind (prolog-find-unmatched-paren nil))
                ))
          

          ;; Return the indentation level
          ind
          ))))))

(defun prolog-find-indent-of-matching-paren ()
  "Find the indentation level based on the matching parenthesis.
Indentation level is set to the one the point is after when the function is
called."
  (save-excursion
    ;; Go to the matching paren
    (if prolog-use-prolog-tokenizer-flag
        (prolog-backward-list)
      (backward-list))

    ;; If this was the first paren on the line then return this line's
    ;; indentation level
    (if (prolog-paren-is-the-first-on-line-p)
        (prolog-indentation-level-of-line)
      ;; It was not the first one
      (progn
         ;; Find the next paren
         (prolog-goto-next-paren 0)

         ;; If this paren is a left one then use its column as indent level,
         ;; if not then recurse this function
         (if (looking-at prolog-left-paren)
             (+ (current-column) 1)
           (progn
              (forward-char 1)
              (prolog-find-indent-of-matching-paren)))
         ))
    ))

(defun prolog-indentation-level-of-line ()
  "Return the indentation level of the current line."
  (save-excursion
    (beginning-of-line)
    (skip-chars-forward " \t")
    (current-column)))

(defun prolog-first-pos-on-line ()
  "Return the first position on the current line."
  (save-excursion
    (beginning-of-line)
    (point)))

(defun prolog-paren-is-the-first-on-line-p ()
  "Return t if the parenthesis under the point is the first one on the line.
Return nil otherwise.
Note: does not check if the point is actually at a parenthesis!"
  (save-excursion
    (let ((begofline (prolog-first-pos-on-line)))
      (if (= begofline (point))
          t
        (if (prolog-goto-next-paren begofline)
            nil
          t)))))

(defun prolog-find-unmatched-paren (&optional mode)
  "Return the column of the last unmatched left parenthesis.
If MODE is `skipwhite' then any white space after the parenthesis is added to
the answer.
If MODE is `plusone' then the parenthesis' column +1 is returned.
If MODE is `termdependent' then if the unmatched parenthesis is part of
a compound term the function will work as `skipwhite', otherwise
it will return the column paren plus the value of `prolog-paren-indent'.
If MODE is nil or not set then the parenthesis' exact column is returned."
  (save-excursion
    ;; If the next paren we find is a left one we're finished, if it's
    ;; a right one then we go back one step and recurse
    (prolog-goto-next-paren 0)

    (let ((roundparen (looking-at "(")))
      (if (looking-at prolog-left-paren)
          (let ((not-part-of-term 
                 (save-excursion
                   (backward-char 1)
                   (looking-at "[ \t]"))))
            (if (eq mode nil)
                (current-column)
              (if (and roundparen
                       (eq mode 'termdependent) 
                       not-part-of-term)
                  (+ (current-column)
                     (if prolog-electric-tab-flag
                         ;; Electric TAB
                         prolog-paren-indent
                       ;; Not electric TAB
                       (if (looking-at ".[ \t]*$")
                           2
                         prolog-paren-indent))
                     )

                (forward-char 1)
                (if (or (eq mode 'skipwhite) (eq mode 'termdependent) )
                    (skip-chars-forward " \t"))
                (current-column))))
        ;; Not looking at left paren
        (progn
          (forward-char 1)
          ;; Go to the matching paren. When we get there we have a total
          ;; balance of 0.
          (if prolog-use-prolog-tokenizer-flag
              (prolog-backward-list)
            (backward-list))
          (prolog-find-unmatched-paren mode)))
      )))


(defun prolog-paren-balance ()
  "Return the parenthesis balance of the current line.
A return value of n means n more left parentheses than right ones."
  (save-excursion
    (end-of-line)
    (prolog-region-paren-balance (prolog-first-pos-on-line) (point))))

(defun prolog-region-paren-balance (beg end)
  "Return the summed parenthesis balance in the region.
The region is limited by BEG and END positions."
  (save-excursion
    (let ((state (if prolog-use-prolog-tokenizer-flag
                     (prolog-tokenize beg end)
                   (parse-partial-sexp beg end))))
      (nth 0 state))))

(defun prolog-goto-next-paren (limit-pos)
  "Move the point to the next parenthesis earlier in the buffer.
Return t if a match was found before LIMIT-POS.  Return nil otherwise."
  (let (retval)
    (setq retval (re-search-backward
                  (concat prolog-left-paren "\\|" prolog-right-paren)
                  limit-pos t))

    ;; If a match was found but it was in a string or comment, then recurse
    (if (and retval (prolog-in-string-or-comment))
        (prolog-goto-next-paren limit-pos)
      retval)
    ))

(defun prolog-in-string-or-comment ()
  "Check whether string, atom, or comment is under current point.
Return:
 `txt' if the point is in a string, atom, or character code expression
 `cmt' if the point is in a comment
 nil otherwise."
  (save-excursion
    (let* ((start
            (if (eq prolog-parse-mode 'beg-of-line)
                ;; 'beg-of-line
                (save-excursion
                  (let (safepoint)
                    (beginning-of-line)
                    (setq safepoint (point))
                    (while (and (> (point) (point-min))
                                (progn
                                  (forward-line -1)
                                  (end-of-line)
                                  (if (not (bobp))
                                      (backward-char 1))
                                  (looking-at "\\\\"))
                                )
                      (beginning-of-line)
                      (setq safepoint (point)))
                    safepoint))
              ;; 'beg-of-clause
              (prolog-clause-start)))
           (end (point))
           (state (if prolog-use-prolog-tokenizer-flag
                      (prolog-tokenize start end)
                    (parse-partial-sexp start end))))
      (cond
       ((nth 3 state) 'txt) ; String
       ((nth 4 state) 'cmt) ; Comment
       (t
        (cond
         ((looking-at "%") 'cmt) ; Start of a comment
         ((looking-at "/\\*") 'cmt) ; Start of a comment
         ((looking-at "\'") 'txt) ; Start of an atom
         ((looking-at "\"") 'txt) ; Start of a string
         (t nil)
         ))))
    ))

(defun prolog-find-start-of-mline-comment ()
  "Return the start column of a /* */ comment.
This assumes that the point is inside a comment."
  (re-search-backward "/\\*" (point-min) t)
  (forward-char 2)
  (skip-chars-forward " \t")
  (current-column))

(defun prolog-insert-spaces-after-paren ()
  "Insert spaces after the opening parenthesis.
Spaces are inserted if the parenthesis is the first non-white character
on the line."
  (save-excursion
    (let (incr level)
      (beginning-of-line)
      (skip-chars-forward " \t")
      (if (looking-at (format "(\\|%s" prolog-left-indent-regexp))
          (progn
            ;; Treat "( If -> " lines specially.
            (if (looking-at "(.*->")
                (setq incr 2)
              (setq incr prolog-paren-indent))
            
            ;; Goto the first char after the matched text
            (re-search-forward (format "(\\|%s" prolog-left-indent-regexp)
                               (point-max) t)
            (goto-char (match-end 0))
            
            (setq level (+ (prolog-find-unmatched-paren) incr))

            ;; Remove old white space
            (let ((start (point)))
              (skip-chars-forward " \t")
              (delete-region start (point)))
            
            (indent-to level)
            ))))
  (skip-chars-forward " \t"))


;;-------------------------------------------------------------------
;; The tokenizer
;;-------------------------------------------------------------------

(defconst prolog-tokenize-searchkey
  (concat "[0-9]+'"
          "\\|"
          "['\"]"
          "\\|"
          prolog-left-paren
          "\\|"
          prolog-right-paren
          "\\|"
          "%"
          "\\|"
          "/\\*"
          ))

(defun prolog-tokenize (beg end &optional stopcond)
  "Tokenize a region of prolog code between BEG and END.
STOPCOND decides the stop condition of the parsing. Valid values
are 'zerodepth which stops the parsing at the first right parenthesis
where the parenthesis depth is zero, 'skipover which skips over
the current entity (e.g. a list, a string, etc.) and nil.

The function returns a list with the following information:
 0. parenthesis depth 
 3. 'atm if END is inside an atom
    'str if END is inside a string
    'chr if END is in a character code expression (0'x)
    nil otherwise
 4. non-nil if END is inside a comment
 5. end position (always equal to END if STOPCOND is nil)
The rest of the elements are undefined."
  (save-excursion
    (let* ((end2 (1+ end))
           oldp
           (depth 0)
           (quoted nil)
           inside_cmt
           (endpos end2)
           skiptype ; The type of entity we'll skip over
           )
      (goto-char beg)

      (if (and (eq stopcond 'skipover)
               (looking-at "[^[({'\"]"))
          (setq endpos (point))                ; Stay where we are
        (while (and
                (re-search-forward prolog-tokenize-searchkey end2 t)
                (< (point) end2))
          (progn
            (setq oldp (point))
            (goto-char (match-beginning 0))
            (cond
             ;; Atoms and strings
             ((looking-at "'")
              ;; Find end of atom
              (if (re-search-forward "[^\\]'" end2 'limit)
                  ;; Found end of atom
                  (progn
                    (setq oldp end2)
                    (if (and (eq stopcond 'skipover)
                             (not skiptype))
                        (setq endpos (point))
                      (setq oldp (point)))) ; Continue tokenizing
                (setq quoted 'atm)))
           
             ((looking-at "\"")
              ;; Find end of string
              (if (re-search-forward "[^\\]\"" end2 'limit)
                  ;; Found end of string
                  (progn
                    (setq oldp end2)
                    (if (and (eq stopcond 'skipover)
                             (not skiptype))
                        (setq endpos (point))
                      (setq oldp (point)))) ; Continue tokenizing
                (setq quoted 'str)))

             ;; Paren stuff
             ((looking-at prolog-left-paren)
              (setq depth (1+ depth))
              (setq skiptype 'paren))

             ((looking-at prolog-right-paren)
              (setq depth (1- depth))
              (if (and
                   (or (eq stopcond 'zerodepth)
                       (and (eq stopcond 'skipover) 
                            (eq skiptype 'paren)))
                   (= depth 0))
                  (progn
                    (setq endpos (1+ (point)))
                    (setq oldp end2))))

             ;; Comment stuff
             ((looking-at comment-start)
              (end-of-line)
              ;; (if (>= (point) end2)
              (if (>= (point) end)
                  (progn
                    (setq inside_cmt t)
                    (setq oldp end2))
                (setq oldp (point))))

             ((looking-at "/\\*")
              (if (re-search-forward "\\*/" end2 'limit)
                  (setq oldp (point))
                (setq inside_cmt t)
                (setq oldp end2)))

             ;; 0'char
             ((looking-at "0'")
              (setq oldp (1+ (match-end 0)))
              (if (> oldp end) 
                  (setq quoted 'chr)))
           
             ;; base'number
             ((looking-at "[0-9]+'")
              (goto-char (match-end 0))
              (skip-chars-forward "0-9a-zA-Z")
              (setq oldp (point)))

             
             )
            (goto-char oldp)
            ))                                ; End of while
        )

      ;; Create return list
      (list depth nil nil quoted inside_cmt endpos)
      )))


;;-------------------------------------------------------------------
;; Online help
;;-------------------------------------------------------------------

(defvar prolog-help-function
  '((mercury nil)
    (eclipse prolog-help-online)
    ;; (sicstus prolog-help-info)
    (sicstus prolog-find-documentation)
    (swi prolog-help-online)
    (t prolog-help-online))
  "Alist for the name of the function for finding help on a predicate.")

(defun prolog-help-on-predicate ()
  "Invoke online help on the atom under cursor."
  (interactive)

  (cond
   ;; Redirect help for SICStus to `prolog-find-documentation'.
   ((eq prolog-help-function-i 'prolog-find-documentation)
    (prolog-find-documentation))

   ;; Otherwise, ask for the predicate name and then call the function
   ;; in prolog-help-function-i
   (t
    (let* (word
           predicate
           ;point
           )
      (setq word (prolog-atom-under-point))
      (setq predicate (read-from-minibuffer
                       (format "Help on predicate%s: "
                               (if word
                                   (concat " (default " word ")")
                                 ""))))
      (if (string= predicate "")
          (setq predicate word))
      (if prolog-help-function-i
          (funcall prolog-help-function-i predicate)
        (error "Sorry, no help method defined for this Prolog system."))))
   ))

(defun prolog-help-info (predicate)
  (let ((buffer (current-buffer))
        oldp
        (str (concat "^\\* " (regexp-quote predicate) " */")))
    (require 'info)
    (pop-to-buffer nil)
    (Info-goto-node prolog-info-predicate-index)
    (if (not (re-search-forward str nil t))
        (error (format "Help on predicate `%s' not found." predicate)))

    (setq oldp (point))
    (if (re-search-forward str nil t)
        ;; Multiple matches, ask user
        (let ((max 2)
              n)
          ;; Count matches
          (while (re-search-forward str nil t)
            (setq max (1+ max)))

          (goto-char oldp)
          (re-search-backward "[^ /]" nil t)
          (recenter 0)
          (setq n (read-input 
                   (format "Several matches, choose (1-%d): " max) "1"))
          (forward-line (- (string-to-number n) 1)))
      ;; Single match
      (re-search-backward "[^ /]" nil t))

    ;; (Info-follow-nearest-node (point))
    (prolog-Info-follow-nearest-node)
    (re-search-forward (concat "^`" (regexp-quote predicate)) nil t)
    (beginning-of-line)
    (recenter 0)
    (pop-to-buffer buffer)))

(defun prolog-Info-follow-nearest-node ()
  (if (eq prolog-emacs 'xemacs)
	(Info-follow-nearest-node (point))
      (Info-follow-nearest-node))
)

(defun prolog-help-online (predicate)
  (prolog-ensure-process)
  (process-send-string "prolog" (concat "help(" predicate ").\n"))
  (display-buffer "*prolog*"))

(defun prolog-help-apropos (string)
  "Find Prolog apropos on given STRING.
This function is only available when `prolog-system' is set to `swi'."
  (interactive "sApropos: ")
  (cond
   ((eq prolog-system 'swi)
    (prolog-ensure-process)
    (process-send-string "prolog" (concat "apropos(" string ").\n"))
    (display-buffer "*prolog*"))
   (t
    (error "Sorry, no Prolog apropos available for this Prolog system."))))

(defun prolog-atom-under-point ()
  "Return the atom under or left to the point."
  (save-excursion
    (let ((nonatom_chars "[](){},\. \t\n")
          start)
      (skip-chars-forward (concat "^" nonatom_chars))
      (skip-chars-backward nonatom_chars)
      (skip-chars-backward (concat "^" nonatom_chars))
      (setq start (point))
      (skip-chars-forward (concat "^" nonatom_chars))
      (buffer-substring-no-properties start (point))
      )))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Help function with completion
;; Stolen from Per Mildner's SICStus debugger mode and modified

(defun prolog-find-documentation ()
  "Go to the Info node for a predicate in the SICStus Info manual."
  (interactive)
  (let ((pred (prolog-read-predicate)))
    (prolog-goto-predicate-info pred)))

(defvar prolog-info-alist nil 
  "Alist with all builtin predicates.
Only for internal use by `prolog-find-documentation'")

;; Very similar to prolog-help-info except that that function cannot
;; cope with arity and that it asks the user if there are several
;; functors with different arity. This function also uses
;; prolog-info-alist for finding the info node, rather than parsing
;; the predicate index.
(defun prolog-goto-predicate-info (predicate)
  "Go to the info page for PREDICATE, which is a PredSpec."
  (interactive)
  (require 'info)
  (string-match "\\(.*\\)/\\([0-9]+\\).*$" predicate)
  (let ((buffer (current-buffer))
        (name (match-string 1 predicate))
        (arity (match-string 2 predicate))
        ;oldp
        ;(str (regexp-quote predicate))
        )
    (setq arity (string-to-number arity))
    (pop-to-buffer nil)

    (Info-goto-node 
     prolog-info-predicate-index) ;; We must be in the SICStus pages
    (Info-goto-node (car (cdr (assoc predicate prolog-info-alist))))

    (prolog-find-term (regexp-quote name) arity "^`")

    (recenter 0)
    (pop-to-buffer buffer))
)

(defun prolog-read-predicate ()
  "Read a PredSpec from the user.
Returned value is a string \"FUNCTOR/ARITY\".
Interaction supports completion."
  (let ((initial (prolog-atom-under-point))
        answer)
    ;; If the predicate index is not yet built, do it now 
    (if (not prolog-info-alist) 
        (prolog-build-info-alist))
    ;; Test if the initial string could be the base for completion.
    ;; Discard it if not.
    (if (eq (try-completion initial prolog-info-alist) nil)
        (setq initial ""))
    ;; Read the PredSpec from the user
    (setq answer (completing-read 
                  "Help on predicate: "
                  prolog-info-alist nil t initial))
    (if (equal answer "")
        initial
      answer)))

(defun prolog-build-info-alist (&optional verbose)
  "Build an alist of all builtins and library predicates. 
Each element is of the form (\"NAME/ARITY\" . (INFO-NODE1 INFO-NODE2 ...)).
Typically there is just one Info node associated with each name
If an optional argument VERBOSE is non-nil, print messages at the beginning
and end of list building."
  (if verbose
      (message "Building info alist..."))
  (setq prolog-info-alist
        (let ((l ())
              (last-entry (cons "" ())))
          (save-excursion
            (save-window-excursion
              ;; select any window but the minibuffer (as we cannot switch
              ;; buffers in minibuffer window.
              ;; I am not sure this is the right/best way
              (if (active-minibuffer-window)  ; nil if none active
                  (select-window (next-window)))
              ;; Do this after going away from minibuffer window
              (save-window-excursion
                (info))
              (Info-goto-node prolog-info-predicate-index)
              (goto-char (point-min))
              (while (re-search-forward
                      "^\\* \\(.+\\)/\\([0-9]+\\)\\([^\n:*]*\\):" nil t)
                (let* ((name (match-string 1))
                       (arity (string-to-int (match-string 2)))
                       (comment (match-string 3))
                       (fa (format "%s/%d%s" name arity comment))
                       info-node)
                  (beginning-of-line)
                  ;; Extract the info node name
                  (setq info-node (progn 
                                    (re-search-forward ":[ \t]*\\([^:]+\\).$")
                                    (match-string 1)
                                   ))
                  ;; ###### Easier? (from Milan version 0.1.28)
                  ;; (setq info-node (Info-extract-menu-node-name))
                  (if (equal fa (car last-entry))
                      (setcdr last-entry (cons info-node (cdr last-entry)))
                    (setq last-entry (cons fa (list info-node))
                          l (cons last-entry l)))))
              (nreverse l)
              ))))
  (if verbose
      (message "Building info alist... done.")))


;;-------------------------------------------------------------------
;; Miscellaneous functions
;;-------------------------------------------------------------------

;; For Windows. Change backslash to slash. SICStus handles either
;; path separator but backslash must be doubled, therefore use slash.
(defun prolog-bsts (string)
  "Change backslashes to slashes in STRING."
  (let ((str1 (copy-sequence string))
        (len (length string))
        (i 0))
    (while (< i len)
      (if (char-equal (aref str1 i) ?\\)
          (aset str1 i ?/))
      (setq i (1+ i)))
    str1))

(defun prolog-temporary-file ()
  "Make temporary file name for compilation."
  (make-temp-name 
   (concat 
    (or
     (getenv "TMPDIR")
     (getenv "TEMP") 
     (getenv "TMP")
     (getenv "SYSTEMP")
     "/tmp")
    "/prolcomp")))
(setq prolog-temp-filename (prolog-bsts (prolog-temporary-file)))

(defun prolog-goto-prolog-process-buffer ()
  "Switch to the prolog process buffer and go to its end."
  (switch-to-buffer-other-window "*prolog*")
  (goto-char (point-max))
)

(defun prolog-enable-sicstus-sd ()
  "Enable the source level debugging facilities of SICStus 3.7 and later."
  (interactive)
  (require 'pltrace) ; Load the SICStus debugger code
  ;; Turn on the source level debugging by default
  (add-hook 'prolog-inferior-mode-hook 'pltrace-on)
  (if (not prolog-use-sicstus-sd)
      (progn
        ;; If there is a *prolog* buffer, then call pltrace-on
        (if (get-buffer "*prolog*")
            ;; Avoid compilation warnings by using eval
            (eval '(pltrace-on)))
        (setq prolog-use-sicstus-sd t)
        ))
  )

(defun prolog-disable-sicstus-sd ()
  "Disable the source level debugging facilities of SICStus 3.7 and later."
  (interactive)
  (setq prolog-use-sicstus-sd nil)
  ;; Remove the hook
  (remove-hook 'prolog-inferior-mode-hook 'pltrace-on)
  ;; If there is a *prolog* buffer, then call pltrace-off
  (if (get-buffer "*prolog*")
      ;; Avoid compile warnings by using eval
      (eval '(pltrace-off))))

(defun prolog-debug-on (&optional arg)
  "Enable debugging.
When called with prefix argument ARG, disable debugging instead."
  (interactive "P")
  (if arg
      (prolog-debug-off)
    (prolog-process-insert-string (get-process "prolog")
                                  prolog-debug-on-string)
    (process-send-string "prolog" prolog-debug-on-string)))

(defun prolog-debug-off ()
  "Disable debugging."
  (interactive)
  (prolog-process-insert-string (get-process "prolog")
                                prolog-debug-off-string)
  (process-send-string "prolog" prolog-debug-off-string))

(defun prolog-trace-on (&optional arg)
  "Enable tracing.
When called with prefix argument ARG, disable tracing instead."
  (interactive "P")
  (if arg
      (prolog-trace-off)
    (prolog-process-insert-string (get-process "prolog")
                                  prolog-trace-on-string)
    (process-send-string "prolog" prolog-trace-on-string)))

(defun prolog-trace-off ()
  "Disable tracing."
  (interactive)
  (prolog-process-insert-string (get-process "prolog")
                                prolog-trace-off-string)
  (process-send-string "prolog" prolog-trace-off-string))

(defun prolog-zip-on (&optional arg)
  "Enable zipping (for SICStus 3.7 and later).
When called with prefix argument ARG, disable zipping instead."
  (interactive "P")
  (if arg
      (prolog-zip-off)
    (prolog-process-insert-string (get-process "prolog")
                                  prolog-zip-on-string)
    (process-send-string "prolog" prolog-zip-on-string)))

(defun prolog-zip-off ()
  "Disable zipping (for SICStus 3.7 and later)."
  (interactive)
  (prolog-process-insert-string (get-process "prolog")
                                prolog-zip-off-string)
  (process-send-string "prolog" prolog-zip-off-string))

;; (defun prolog-create-predicate-index ()
;;   "Create an index for all predicates in the buffer."
;;   (let ((predlist '())
;;         clauseinfo 
;;         object
;;         pos
;;         )
;;     (goto-char (point-min))
;;     ;; Replace with prolog-clause-start!
;;     (while (re-search-forward "^.+:-" nil t)
;;       (setq pos (match-beginning 0))
;;       (setq clauseinfo (prolog-clause-info))
;;       (setq object (prolog-in-object))
;;       (setq predlist (append
;;                       predlist
;;                       (list (cons 
;;                              (if (and (eq prolog-system 'sicstus)
;;                                       (prolog-in-object))
;;                                  (format "%s::%s/%d" 
;;                                          object
;;                                          (nth 0 clauseinfo) 
;;                                          (nth 1 clauseinfo))
;;                                (format "%s/%d"
;;                                        (nth 0 clauseinfo) 
;;                                        (nth 1 clauseinfo)))
;;                              pos
;;                              ))))
;;       (prolog-end-of-predicate))
;;     predlist))

(defun prolog-get-predspec ()
  (save-excursion
    (let ((state (prolog-clause-info))
          (object (prolog-in-object)))
      (if (equal (nth 0 state) "")
          nil
        (if (and (eq prolog-system 'sicstus)
                 object)
            (format "%s::%s/%d" 
                    object
                    (nth 0 state) 
                    (nth 1 state))
          (format "%s/%d"
                  (nth 0 state) 
                  (nth 1 state)))
        ))))

;; For backward compatibility. Stolen from custom.el.
(or (fboundp 'match-string)
    ;; Introduced in Emacs 19.29.
    (defun match-string (num &optional string)
  "Return string of text matched by last search.
NUM specifies which parenthesized expression in the last regexp.
 Value is nil if NUMth pair didn't match, or there were less than NUM pairs.
Zero means the entire text matched by the whole regexp or whole string.
STRING should be given if the last search was by `string-match' on STRING."
  (if (match-beginning num)
      (if string
          (substring string (match-beginning num) (match-end num))
        (buffer-substring (match-beginning num) (match-end num))))))

(defun prolog-pred-start ()
  "Return the starting point of the first clause of the current predicate."
  (save-excursion
    (goto-char (prolog-clause-start))
    ;; Find first clause, unless it was a directive
    (if (and (not (looking-at "[:?]-"))
             (not (looking-at "[ \t]*[%/]"))) ; Comment
        (let* ((pinfo (prolog-clause-info))
               (predname (nth 0 pinfo))
               (arity (nth 1 pinfo))
               (op (point)))
          (while (and (re-search-backward
                       (format "^%s\\([(\\.]\\| *%s\\)" 
                               predname prolog-head-delimiter) nil t)
                      (= arity (nth 1 (prolog-clause-info)))
                      )
            (setq op (point)))
          (if (eq prolog-system 'mercury)
              ;; Skip to the beginning of declarations of the predicate
              (progn
                (goto-char (prolog-beginning-of-clause))
                (while (and (not (eq (point) op))
                            (looking-at
                             (format ":-[ \t]*\\(pred\\|mode\\)[ \t]+%s"
                                     predname)))
                  (setq op (point))
                  (goto-char (prolog-beginning-of-clause)))))
          op)
      (point))))

(defun prolog-pred-end ()
  "Return the position at the end of the last clause of the current predicate."
  (save-excursion
    (goto-char (prolog-clause-end))        ; if we are before the first predicate
    (goto-char (prolog-clause-start))
    (let* ((pinfo (prolog-clause-info))
          (predname (nth 0 pinfo))
          (arity (nth 1 pinfo))
          oldp
          (notdone t)
          (op (point)))
      (if (looking-at "[:?]-")
          ;; This was a directive
          (progn
            (if (and (eq prolog-system 'mercury)
                     (looking-at
                      (format ":-[ \t]*\\(pred\\|mode\\)[ \t]+\\(%s+\\)"
                              prolog-atom-regexp)))
                ;; Skip predicate declarations
                (progn
                  (setq predname (buffer-substring-no-properties
                                  (match-beginning 2) (match-end 2)))
                  (while (re-search-forward
                          (format
                           "\n*\\(:-[ \t]*\\(pred\\|mode\\)[ \t]+\\)?%s[( \t]"
                           predname)
                          nil t))))
            (goto-char (prolog-clause-end))
            (setq op (point)))
        ;; It was not a directive, find the last clause
        (while (and notdone
                    (re-search-forward
                     (format "^%s\\([(\\.]\\| *%s\\)" 
                             predname prolog-head-delimiter) nil t)
                    (= arity (nth 1 (prolog-clause-info))))
          (setq oldp (point))
          (setq op (prolog-clause-end))
          (if (>= oldp op)
              ;; End of clause not found.
              (setq notdone nil)
            ;; Continue while loop
            (goto-char op))))
      op)))

(defun prolog-clause-start (&optional not-allow-methods)
  "Return the position at the start of the head of the current clause.
If NOTALLOWMETHODS is non-nil then do not match on methods in
objects (relevent only if 'prolog-system' is set to 'sicstus)."
  (save-excursion
    (let ((notdone t)
          (retval (point-min)))
      (end-of-line)
      
      ;; SICStus object?
      (if (and (not not-allow-methods)
               (eq prolog-system 'sicstus)
               (prolog-in-object))
          (while (and 
                  notdone 
                  ;; Search for a head or a fact
                  (re-search-backward
                   ;; If in object, then find method start.
                   ;; "^[ \t]+[a-z$].*\\(:-\\|&\\|:: {\\|,\\)" 
                   "^[ \t]+[a-z$].*\\(:-\\|&\\|:: {\\)" ; The comma causes
                                        ; problems since we cannot assume
                                        ; that the line starts at column 0,
                                        ; thus we don't know if the line
                                        ; is a head or a subgoal
                   (point-min) t))
            (if (>= (prolog-paren-balance) 0) ; To no match on "   a) :-"
                ;; Start of method found
                (progn
                  (setq retval (point))
                  (setq notdone nil)))
            )                                ; End of while

        ;; Not in object
        (while (and 
                notdone 
                ;; Search for a text at beginning of a line
                ;; ######
                ;; (re-search-backward "^[a-z$']" nil t))
                (re-search-backward
                 ;; (format "^[%s$']" prolog-lower-case-string)
                 (format "^\\([%s$']\\|[:?]-\\)" prolog-lower-case-string)
                 nil t))
          (let ((bal (prolog-paren-balance)))
            (cond
             ((> bal 0)
              ;; Start of clause found
              (progn
                (setq retval (point))
                (setq notdone nil)))
             ((and (= bal 0)
                   (looking-at
                    (format ".*\\(\\.\\|%s\\|!,\\)[ \t]*\\(%%.*\\|\\)$" 
                            prolog-head-delimiter)))
              ;; Start of clause found if the line ends with a '.' or
              ;; a prolog-head-delimiter
              (progn
                (setq retval (point))
                (setq notdone nil))
              )
             (t nil) ; Do nothing
             ))))
                
        retval)))

(defun prolog-clause-end (&optional not-allow-methods)
  "Return the position at the end of the current clause.
If NOTALLOWMETHODS is non-nil then do not match on methods in
objects (relevent only if 'prolog-system' is set to 'sicstus)."
  (save-excursion
    (beginning-of-line)                ; Necessary since we use "^...." for the search
    (if (re-search-forward 
         (if (and (not not-allow-methods)
                  (eq prolog-system 'sicstus)
                  (prolog-in-object))
             (format
              "^\\(%s\\|%s\\|[^\n\'\"%%]\\)*&[ \t]*\\(\\|%%.*\\)$\\|[ \t]*}"
              prolog-quoted-atom-regexp prolog-string-regexp)
           (format
            "^\\(%s\\|%s\\|[^\n\'\"%%]\\)*\\.[ \t]*\\(\\|%%.*\\)$"
            prolog-quoted-atom-regexp prolog-string-regexp))
         nil t)
        (if (and (prolog-in-string-or-comment)
                 (not (eobp)))
            (progn
              (forward-char)
              (prolog-clause-end))
          (point))
      (point))))

(defun prolog-clause-info ()
  "Return a (name arity) list for the current clause."
  (let (predname (arity 0))
    (save-excursion
      (goto-char (prolog-clause-start))
      (let ((op (point)))
        (if (looking-at prolog-atom-char-regexp)
            (progn
              (skip-chars-forward "^ (\\.")
              (setq predname (buffer-substring op (point))))
          (setq predname ""))
        ;; Retrieve the arity
        (if (looking-at prolog-left-paren)
            (let ((endp (save-excursion
                          (prolog-forward-list) (point))))
              (setq arity 1)
              (forward-char 1)                ; Skip the opening paren
              (while (progn
                       (skip-chars-forward "^[({,'\"")
                       (< (point) endp))
                (if (looking-at ",")
                    (progn
                      (setq arity (1+ arity))
                      (forward-char 1)        ; Skip the comma
                      )
                  ;; We found a string, list or something else we want
                  ;; to skip over. Always use prolog-tokenize,
                  ;; parse-partial-sexp does not have a 'skipover mode.
                  (goto-char (nth 5 (prolog-tokenize (point) endp 'skipover))))
                )))
        (list predname arity)
        ))))

(defun prolog-in-object ()
  "Return object name if the point is inside a SICStus object definition."
  ;; Return object name if the last line that starts with a character
  ;; that is neither white space nor a comment start
  (save-excursion
    (if (save-excursion 
          (beginning-of-line)
          (looking-at "\\([^\n ]+\\)[ \t]*::[ \t]*{"))
        ;; We were in the head of the object
        (match-string 1)
      ;; We were not in the head
      (if (and (re-search-backward "^[a-z$'}]" nil t)
               (looking-at "\\([^\n ]+\\)[ \t]*::[ \t]*{"))
          (match-string 1)
        nil))))

(defun prolog-forward-list ()
  "Move the point to the matching right parenthesis."
  (interactive)
  (if prolog-use-prolog-tokenizer-flag
      (let ((state (prolog-tokenize (point) (point-max) 'zerodepth)))
        (goto-char (nth 5 state)))
    (forward-list)))

;; NB: This could be done more efficiently!
(defun prolog-backward-list ()
  "Move the point to the matching left parenthesis."
  (interactive)
  (if prolog-use-prolog-tokenizer-flag
      (let ((bal 0)
            (paren-regexp (concat prolog-left-paren "\\|" prolog-right-paren))
            (notdone t))
        (while (and notdone (re-search-backward paren-regexp nil t))
          (cond
           ((looking-at prolog-left-paren)
            (if (not (prolog-in-string-or-comment))
                (setq bal (1+ bal)))
            (if (= bal 0)
                (setq notdone nil)))
           ((looking-at prolog-right-paren)
            (if (not (prolog-in-string-or-comment))
                (setq bal (1- bal))))
           )))
    (backward-list)))

(defun prolog-beginning-of-clause ()
  "Move to the beginning of current clause.
If already at the beginning of clause, move to previous clause."
  (interactive)
  (let ((point (point))
        (new-point (prolog-clause-start)))
    (if (and (>= new-point point)
             (> point 1))
        (progn
          (goto-char (1- point))
          (goto-char (prolog-clause-start)))
      (goto-char new-point)
      (skip-chars-forward " \t"))))

;; (defun prolog-previous-clause ()
;;   "Move to the beginning of the previous clause."
;;   (interactive)
;;   (forward-char -1)
;;   (prolog-beginning-of-clause))

(defun prolog-end-of-clause ()
  "Move to the end of clause.
If already at the end of clause, move to next clause."
  (interactive)
  (let ((point (point))
        (new-point (prolog-clause-end)))
    (if (and (<= new-point point)
             (not (eq new-point (point-max))))
        (progn
          (goto-char (1+ point))
          (goto-char (prolog-clause-end)))
      (goto-char new-point))))

;; (defun prolog-next-clause ()
;;   "Move to the beginning of the next clause."
;;   (interactive)
;;   (prolog-end-of-clause)
;;   (forward-char)
;;   (prolog-end-of-clause)
;;   (prolog-beginning-of-clause))

(defun prolog-beginning-of-predicate ()
  "Go to the nearest beginning of predicate before current point.
Return the final point or nil if no such a beginning was found."
  (interactive)
  (let ((op (point))
        (pos (prolog-pred-start)))
    (if pos
        (if (= op pos)
            (if (not (bobp))
                (progn
                  (goto-char pos)
                  (backward-char 1)
                  (setq pos (prolog-pred-start))
                  (if pos
                      (progn
                        (goto-char pos)
                        (point)))))
          (goto-char pos)
          (point)))))

(defun prolog-end-of-predicate ()
  "Go to the end of the current predicate."
  (interactive)
  (let ((op (point)))
    (goto-char (prolog-pred-end))
    (if (= op (point))
        (progn
          (forward-line 1)
          (prolog-end-of-predicate)))))

(defun prolog-insert-predspec ()
  "Insert the predspec for the current predicate."
  (interactive)
  (let* ((pinfo (prolog-clause-info))
         (predname (nth 0 pinfo))
         (arity (nth 1 pinfo)))
    (insert (format "%s/%d" predname arity))))

(defun prolog-view-predspec ()
  "Insert the predspec for the current predicate."
  (interactive)
  (let* ((pinfo (prolog-clause-info))
         (predname (nth 0 pinfo))
         (arity (nth 1 pinfo)))
    (message (format "%s/%d" predname arity))))

(defun prolog-insert-predicate-template ()
  "Insert the template for the current clause."
  (interactive)
  (let* ((n 1)
         oldp
         (pinfo (prolog-clause-info))
         (predname (nth 0 pinfo))
         (arity (nth 1 pinfo)))
    (insert predname)
    (if (> arity 0)
        (progn
          (insert "(")
          (setq oldp (point))
          (while (< n arity)
            (insert ",")
            (setq n (1+ n)))
          (insert ")")
          (goto-char oldp)
          ))
  ))

(defun prolog-insert-next-clause ()
  "Insert newline and the name of the current clause."
  (interactive)
  (insert "\n")
  (prolog-insert-predicate-template))

(defun prolog-insert-module-modeline ()
  "Insert a modeline for module specification.
This line should be first in the buffer.
The module name should be written manually just before the semi-colon."
  (interactive)
  (insert "%%% -*- Module: ; -*-\n")
  (backward-char 6))

(defun prolog-uncomment-region (beg end)
  "Uncomment the region between BEG and END."
  (interactive "r")
  (comment-region beg end -1))

(defun prolog-goto-comment-column (&optional nocreate)
  "Move comments on the current line to the correct position.
If NOCREATE is nil (or omitted) and there is no comment on the line, then
a new comment is created."
  (interactive)
  (beginning-of-line)
  (if (or (not nocreate)
          (and
           (re-search-forward 
            (format "^\\(\\(%s\\|%s\\|[^\n\'\"%%]\\)*\\)%% *" 
                    prolog-quoted-atom-regexp prolog-string-regexp)
            (save-excursion (end-of-line) (point)) 'limit)
           (progn
             (goto-char (match-beginning 0))
             (not (eq (prolog-in-string-or-comment) 'txt)))))
      (indent-for-comment)))

(defun prolog-indent-predicate ()
  "*Indent the current predicate."
  (interactive)
  (indent-region (prolog-pred-start) (prolog-pred-end) nil))

(defun prolog-indent-buffer ()
  "*Indent the entire buffer."
  (interactive)
  (indent-region (point-min) (point-max) nil))

(defun prolog-mark-clause ()
  "Put mark at the end of this clause and move point to the beginning."
  (interactive)
  (let ((pos (point)))
    (goto-char (prolog-clause-end))
    (forward-line 1)
    (beginning-of-line)
    (set-mark (point))
    (goto-char pos)
    (goto-char (prolog-clause-start))))

(defun prolog-mark-predicate ()
  "Put mark at the end of this predicate and move point to the beginning."
  (interactive)
  (let (pos)
    (goto-char (prolog-pred-end))
    (setq pos (point))
    (forward-line 1)
    (beginning-of-line)
    (set-mark (point))
    (goto-char pos)
    (goto-char (prolog-pred-start))))

;; Stolen from `cc-mode.el':
(defun prolog-electric-delete (arg)
  "Delete preceding character or whitespace.
If `prolog-hungry-delete-key-flag' is non-nil, then all preceding whitespace is
consumed.  If however an ARG is supplied, or `prolog-hungry-delete-key-flag' is
nil, or point is inside a literal then the function in the variable
`backward-delete-char' is called."
  (interactive "P")
  (if (or (not prolog-hungry-delete-key-flag)
          arg
          (prolog-in-string-or-comment))
      (funcall 'backward-delete-char (prefix-numeric-value arg))
    (let ((here (point)))
      (skip-chars-backward " \t\n")
      (if (/= (point) here)
          (delete-region (point) here)
        (funcall 'backward-delete-char 1)
        ))))

;; For XEmacs compatibility (suggested by Per Mildner)
(put 'prolog-electric-delete 'pending-delete 'supersede)

(defun prolog-electric-dot (arg)
  "Insert dot and newline or a head of a new clause.

If `prolog-electric-dot-flag' is nil, then simply insert dot.
Otherwise::
When invoked at the end of nonempty line, insert dot and newline.
When invoked at the end of an empty line, insert a recursive call to
the current predicate.
When invoked at the beginning of line, insert a head of a new clause
of the current predicate.

When called with prefix argument ARG, insert just dot."
  (interactive "P")
  ;; Check for situations when the electricity should not be active
  (if (or (not prolog-electric-dot-flag)
          arg
          (prolog-in-string-or-comment)
          ;; Do not be electrix in a floating point number or an operator
          (save-excursion 
            (not 
             (re-search-backward
              ;; ######
              ;; "\\(^\\|[])}a-zA-Z_!'0-9]+\\)[ \t]*\\=" nil t)))
              (format "\\(^\\|[])}%s%s_!'0-9]+\\)[ \t]*\\=" 
                      prolog-lower-case-string
                      prolog-upper-case-string)
              nil t)))
          ;; Do not be electric if inside a parenthesis pair.
          (not (= (prolog-region-paren-balance (prolog-clause-start) (point))
                  0))
          )
      (funcall 'self-insert-command (prefix-numeric-value arg))
    (cond
     ;; Beginning of line
     ((bolp)
      (prolog-insert-predicate-template))
     ;; At an empty line with at least one whitespace
     ((save-excursion
        (beginning-of-line)
        (looking-at "[ \t]+$"))
      (prolog-insert-predicate-template)
      (save-excursion 
        (end-of-line)
        (insert ".\n")))
     ;; Default
     (t
      (insert ".\n"))
     )))

(defun prolog-electric-underscore ()
  "Replace variable with an underscore.
If `prolog-electric-underscore-flag' is non-nil and the point is
on a variable then replace the variable with underscore and skip
the following comma and whitespace, if any.
If the point is not on a variable then insert underscore."
  (interactive)
  (if prolog-electric-underscore-flag
      (let (;start
            (oldcase case-fold-search)
            (oldp (point)))
        (setq case-fold-search nil)
        ;; ######
        ;;(skip-chars-backward "a-zA-Z_")
        (skip-chars-backward
         (format "%s%s_" 
                 prolog-lower-case-string 
                 prolog-upper-case-string))

        ;(setq start (point))
        (if (and (not (prolog-in-string-or-comment))
                 ;; ######
                 ;; (looking-at "\\<[_A-Z][a-zA-Z_0-9]*\\>"))
                 (looking-at (format "\\<[_%s][%s%s_0-9]*\\>" 
                                     prolog-upper-case-string
                                     prolog-lower-case-string
                                     prolog-upper-case-string)))
            (progn
              (replace-match "_")
              (skip-chars-forward ", \t\n"))
          (goto-char oldp)
          (self-insert-command 1))
        (setq case-fold-search oldcase)
        )
    (self-insert-command 1))
  )


(defun prolog-find-term (functor arity &optional prefix)
  "Go to the position at the start of the next occurance of a term.
The term is specified with FUNCTOR and ARITY. The optional argument
PREFIX is the prefix of the search regexp."
  (let* (;; If prefix is not set then use the default "\\<"
         (prefix (if (not prefix)
                     "\\<"
                   prefix))
         (regexp (concat prefix functor))
         (i 1))
      
    ;; Build regexp for the search if the arity is > 0
    (if (= arity 0)
        ;; Add that the functor must be at the end of a word. This
        ;; does not work if the arity is > 0 since the closing )
        ;; is not a word constituent.
        (setq regexp (concat regexp "\\>"))
      ;; Arity is > 0, add parens and commas
      (setq regexp (concat regexp "("))
      (while (< i arity)
        (setq regexp (concat regexp ".+,"))
        (setq i (1+ i)))
      (setq regexp (concat regexp ".+)")))
      
    ;; Search, and return position
    (if (re-search-forward regexp nil t)
        (goto-char (match-beginning 0))
      (error "Term not found"))
    ))

(defun prolog-variables-to-anonymous (beg end)
  "Replace all variables within a region BEG to END by anonymous variables."
  (interactive "r")
  (save-excursion
    (let ((oldcase case-fold-search))
      (setq case-fold-search nil)
      (goto-char end)
      (while (re-search-backward "\\<[A-Z_][a-zA-Z_0-9]*\\>" beg t)
        (progn
          (replace-match "_")
          (backward-char)))
      (setq case-fold-search oldcase)
      )))


(defun prolog-set-atom-regexps ()
  "Set the `prolog-atom-char-regexp' and `prolog-atom-regexp' variables.
Must be called after `prolog-build-case-strings'."
  (setq prolog-atom-char-regexp
        (format "[%s%s0-9_$]" 
                prolog-lower-case-string 
                prolog-upper-case-string))
  (setq prolog-atom-regexp
        (format "[%s$]%s*" 
                prolog-lower-case-string 
                prolog-atom-char-regexp))
  )

(defun prolog-build-case-strings ()
  "Set `prolog-upper-case-string' and `prolog-lower-case-string'.
Uses the current case-table for extracting the relevant information."
  (let ((up_string "")
        (low_string ""))
    ;; Use `map-char-table' if it is defined. Otherwise enumerate all
    ;; numbers between 0 and 255. `map-char-table' is probably safer.
    (if (and (not (eq prolog-emacs 'xemacs))
              (fboundp 'map-char-table))
        (map-char-table
         (lambda (key value)
           (cond 
            ((and 
              (eq (int-to-char key) (downcase key))
              (eq (int-to-char key) (upcase key)))
             ;; Do nothing if upper and lower case are the same
             )
            ((eq (int-to-char key) (downcase key))
             ;; The char is lower case
             (setq low_string (format "%s%c" low_string key)))
            ((eq (int-to-char key) (upcase key))
             ;; The char is upper case
             (setq up_string (format "%s%c" up_string key)))
            ))
         (current-case-table))
      ;; `map-char-table' was undefined.
      (let ((key 0))
        (while (< key 256)
          (cond 
           ((and 
             (eq (int-to-char key) (downcase key))
             (eq (int-to-char key) (upcase key)))
            ;; Do nothing if upper and lower case are the same
            )
           ((eq (int-to-char key) (downcase key))
            ;; The char is lower case
            (setq low_string (format "%s%c" low_string key)))
           ((eq (int-to-char key) (upcase key))
            ;; The char is upper case
            (setq up_string (format "%s%c" up_string key)))
           )
          (setq key (1+ key))))
      )
    ;; The strings are single-byte strings
    (setq prolog-upper-case-string up_string)
    (setq prolog-lower-case-string low_string)
    ))

;; FSF Emacs compatibility: FSF Emacs does not differentiate between
;; ints and chars, or at least these two are interchangeable.
(or (fboundp 'int-to-char)
    ;; Introduced in Emacs 19.29.
    (defun int-to-char (num)
      num))


;;-------------------------------------------------------------------
;; Menu stuff (both for the editing buffer and for the inferior
;; prolog buffer)
;;-------------------------------------------------------------------

(unless (fboundp 'region-exists-p)
  (defun region-exists-p ()
    "Non-nil iff the mark is set.  Lobotomized version for Emacsen that do not provide their own."
    (mark)))

(defun prolog-menu ()
  "Creates the menus for the Prolog editing buffers.
These menus are dynamically created because one may change systems
during the life of an Emacs session, and because FSF Emacs wants them
so by ignoring `easy-menu-add'."

  ;; FSF Emacs ignores `easy-menu-add' so the order in which the menus
  ;; are defined _is_ important!

  (easy-menu-define 
   prolog-edit-menu-help (current-local-map)
   "Help menu for the Prolog mode."
   (append
    (if (eq prolog-emacs 'xemacs) '("Help") '("Prolog-help"))
    (cond
     ((eq prolog-system 'sicstus)
      '(["On predicate" prolog-help-on-predicate t]
        "---"))
     ((eq prolog-system 'swi)
      '(["On predicate" prolog-help-on-predicate t]
        ["Apropos" prolog-help-apropos t]
        "---")))
    '(["Describe mode" describe-mode t])))

  (easy-menu-define 
   prolog-edit-menu-runtime (current-local-map) 
   "Runtime Prolog commands available from the editing buffer"
   (append 
    ;; runtime menu name
    (list (cond ((eq prolog-system 'eclipse) 
                 "ECLiPSe")
                ((eq prolog-system 'mercury) 
                 "Mercury")
                (t
                 "Prolog")))
    ;; consult items, NIL for mercury
    (unless (eq prolog-system 'mercury)
      '("---"
        ["Consult file" prolog-consult-file t]
        ["Consult buffer" prolog-consult-buffer t]
        ["Consult region" prolog-consult-region (region-exists-p)]
        ["Consult predicate" prolog-consult-predicate t]
        ))
    ;; compile items, NIL for everything but SICSTUS
    (when (eq prolog-system 'sicstus)
      '("---"
        ["Compile file" prolog-compile-file t]
        ["Compile buffer" prolog-compile-buffer t]
        ["Compile region" prolog-compile-region (region-exists-p)]
        ["Compile predicate" prolog-compile-predicate t]
        ))
    ;; debug items, NIL for mercury
    (cond 
     ((eq prolog-system 'sicstus) 
      ;; In SICStus, these are pairwise disjunctive,
      ;; so it's enough with one "off"-command
      (if (prolog-atleast-version '(3 . 7))
          (list "---"
                ["Debug" prolog-debug-on t]
                ["Trace" prolog-trace-on t]
                ["Zip" prolog-zip-on t]
                ["All debug off" prolog-debug-off t]
                '("Source level debugging"
                  ["Enable" prolog-enable-sicstus-sd t]
                  ["Disable" prolog-disable-sicstus-sd t]))
        (list "---"
              ["Debug" prolog-debug-on t]
              ["Trace" prolog-trace-on t]
              ["All debug off" prolog-debug-off t])))
     ((not (eq prolog-system 'mercury))
      '("---"
        ["Debug" prolog-debug-on t]
        ["Debug off" prolog-debug-off t]
        ["Trace" prolog-trace-on t]
        ["Trace off" prolog-trace-off t]))
     ;; default (mercury) nil
     )
    (unless (eq prolog-system 'mercury)
      (list "---"
            (if (eq prolog-emacs 'xemacs)
                [(concat "Run " (cond ((eq prolog-system 'eclipse) "ECLiPSe")
                                      ((eq prolog-system 'mercury) "Mercury")
                                      (t "Prolog")))
                 run-prolog t]
              ["Run Prolog" run-prolog t])))))

  (easy-menu-define 
    prolog-edit-menu-insert-move (current-local-map) 
    "Commands for Prolog code manipulation."
    (append
     (list "Code"
           ["Comment region" comment-region (region-exists-p)]
           ["Uncomment region" prolog-uncomment-region (region-exists-p)]
           ["Add comment/move to comment" indent-for-comment t])
     (unless (eq prolog-system 'mercury)
       (list ["Convert variables in region to '_'" prolog-variables-to-anonymous (region-exists-p)]))
     (list "---"
           ["Insert predicate template" prolog-insert-predicate-template t]
           ["Insert next clause head" prolog-insert-next-clause t]
           ["Insert predicate spec" prolog-insert-predspec t]
           ["Insert module modeline" prolog-insert-module-modeline t]
           "---"
           ["Beginning of clause" prolog-beginning-of-clause t]
           ["End of clause" prolog-end-of-clause t]
           ["Beginning of predicate" prolog-beginning-of-predicate t]
           ["End of predicate" prolog-end-of-predicate t]
           "---"
           ["Indent line" prolog-indent-line t]
           ["Indent region" indent-region (region-exists-p)]
           ["Indent predicate" prolog-indent-predicate t]
           ["Indent buffer" prolog-indent-buffer t]
           "---"
           ["Mark clause" prolog-mark-clause t]
           ["Mark predicate" prolog-mark-predicate t]
           ["Mark paragraph" mark-paragraph t]
           ;"---"
           ;["Fontify buffer" font-lock-fontify-buffer t]
           )))

  (easy-menu-add prolog-edit-menu-insert-move)
  (easy-menu-add prolog-edit-menu-runtime)
        
  ;; Add predicate index menu
  (make-variable-buffer-local 'imenu-create-index-function)
  (setq imenu-create-index-function 'imenu-default-create-index-function)
  ;;Milan (this has problems with object methods...)  ###### Does it? (Stefan)
  (setq imenu-prev-index-position-function 'prolog-beginning-of-predicate)
  (setq imenu-extract-index-name-function 'prolog-get-predspec)
  
  (if (and prolog-imenu-flag
           (< (count-lines (point-min) (point-max)) prolog-imenu-max-lines))
      (imenu-add-to-menubar "Predicates"))
  
  (easy-menu-add prolog-edit-menu-help))

(defun prolog-inferior-menu ()
  "Creates the menus for the Prolog inferior buffer.
This menu is dynamically created because one may change systems during
the life of an Emacs session."

  (easy-menu-define 
   prolog-inferior-menu-help (current-local-map)
   "Help menu for the Prolog inferior mode."
   (append
    (if (eq prolog-emacs 'xemacs) '("Help") '("Prolog-help"))
    (cond
     ((eq prolog-system 'sicstus)
      '(["On predicate" prolog-help-on-predicate t]
        "---"))
     ((eq prolog-system 'swi)
      '(["On predicate" prolog-help-on-predicate t]
        ["Apropos" prolog-help-apropos t]
        "---")))
    '(["Describe mode" describe-mode t])))

  (easy-menu-define
   prolog-inferior-menu-all (current-local-map)
   "Menu for the inferior Prolog buffer."
   (append
    ;; menu name
    (list (cond ((eq prolog-system 'eclipse) 
                 "ECLiPSe")
                ((eq prolog-system 'mercury) 
                 "Mercury")
                (t
                 "Prolog")))
    ;; debug items, NIL for mercury
    (cond 
     ((eq prolog-system 'sicstus) 
      ;; In SICStus, these are pairwise disjunctive,
      ;; so it's enough with one "off"-command
      (if (prolog-atleast-version '(3 . 7))
          (list "---"
                ["Debug" prolog-debug-on t]
                ["Trace" prolog-trace-on t]
                ["Zip" prolog-zip-on t]
                ["All debug off" prolog-debug-off t]
                '("Source level debugging"
                  ["Enable" prolog-enable-sicstus-sd t]
                  ["Disable" prolog-disable-sicstus-sd t]))
        (list "---"
              ["Debug" prolog-debug-on t]
              ["Trace" prolog-trace-on t]
              ["All debug off" prolog-debug-off t])))
     ((not (eq prolog-system 'mercury))
      '("---"
        ["Debug" prolog-debug-on t]
        ["Debug off" prolog-debug-off t]
        ["Trace" prolog-trace-on t]
        ["Trace off" prolog-trace-off t]))
     ;; default (mercury) nil
     )
    ;; runtime
    '("---"
      ["Interrupt Prolog" comint-interrupt-subjob t]
      ["Quit Prolog" comint-quit-subjob t]
      ["Kill Prolog" comint-kill-subjob t])
    ))

  (easy-menu-add prolog-inferior-menu-all)
  (easy-menu-add prolog-inferior-menu-help))

(add-hook 'prolog-mode-hook 'prolog-menu)
(add-hook 'prolog-inferior-mode-hook 'prolog-inferior-menu)

(add-hook 'prolog-mode-hook '(lambda () (font-lock-mode 1)))
(add-hook 'prolog-inferior-mode-hook '(lambda () (font-lock-mode 1)))


(defun prolog-mode-version ()
  "Echo the current version of Prolog mode in the minibuffer."
  (interactive)
  (message "Using Prolog mode version %s" prolog-mode-version))

(provide 'prolog)

;;; prolog.el ends here