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;; define.jl -- Scheme define syntax
;; Copyright (C) 2000 John Harper <john@dcs.warwick.ac.uk>
;; $Id: define.jl,v 1.32 2001/08/08 06:00:20 jsh Exp $
;; This file is part of librep.
;; librep 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.
;; librep 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 librep; see the file COPYING. If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
(declare (unsafe-for-call/cc))
(declare (in-module rep.lang.interpreter))
(open-structures '(rep.lang.backquote))
;; Commentary:
;; This attempts to implement Scheme's elegant block-structured
;; function definitions. It will scan leading `define' forms from all
;; `define', `let', `let*', and `lambda' special forms (and from any
;; macros in terms of these special forms)
;; Note that the rep interpreter and compiler support scheme-like
;; lambda lists natively, so things like (define (foo . bar) ..) will
;; work correctly
;; Note^2 that this doesn't work quite like Scheme define, in that the
;; outermost define always affects the global environment (unless
;; within a with-internal-definitions block) [the reason for this
;; ugliness is to avoid redefining lambda]
;; List of currently bound variables. Used to avoid expanding macros
;; that have been rebound locally
(%define define-bound-vars (make-fluid '()))
;; returns (SYM DEF [DOC])
(defun define-parse (args)
(if (consp (car args))
(define-parse `(,(caar args) (lambda ,(cdar args) ,@(cdr args))))
(list* (car args) (define-scan-form (cadr args))
(and (stringp (caddr args)) (list (caddr args))))))
(defun define-scan-internals (body)
(let
(defs)
(while (eq (caar body) 'define)
(setq defs (cons (define-parse (cdar body)) defs))
(setq body (cdr body)))
(if defs
(list* 'letrec
(mapcar (lambda (def)
(list (car def) (cadr def))) (nreverse defs))
(define-scan-body body))
(let ((new-body (define-scan-body body)))
(if (null (cdr new-body))
(car new-body)
(cons 'progn new-body))))))
(defun define-scan-body (body)
(let ((new (mapcar define-scan-form body)))
(if (equal new body) body new)))
(defun define-macroexpand-1 (form)
(if (memq (car form) (fluid define-bound-vars))
form
(macroexpand-1 form macro-environment)))
;; This needs to handle all special forms. It also needs to handle any
;; macros that the compiler wants to see without being expanded..
(defun define-scan-form (form)
(if (atom form)
form
(case (if (memq (car form) (fluid define-bound-vars)) '() (car form))
((let)
(if (and (eq (car form) 'let) (cadr form) (symbolp (cadr form)))
;; named let, expand
(define-scan-form (define-macroexpand-1 form))
(let loop ((rest (cadr form))
(vars '())
(clauses '()))
(cond ((null rest)
(list 'let (nreverse clauses)
(let-fluids ((define-bound-vars
(nconc vars (fluid define-bound-vars))))
(define-scan-internals (cddr form)))))
((consp (car rest))
(loop (cdr rest)
(cons (caar rest) vars)
(cons (cons (caar rest)
(define-scan-body (cdar rest))) clauses)))
(t (loop (cdr rest)
(cons (car rest) vars)
(cons (car rest) clauses)))))))
((let*)
(let-fluids ((define-bound-vars (fluid define-bound-vars)))
(let loop ((rest (cadr form))
(clauses '()))
(cond ((null rest)
(list 'let* (nreverse clauses)
(define-scan-internals (cddr form))))
((consp (car rest))
(fluid-set define-bound-vars
(cons (caar rest) (fluid define-bound-vars)))
(loop (cdr rest)
(cons (cons (caar rest)
(define-scan-body (cdar rest))) clauses)))
(t
(fluid-set define-bound-vars
(cons (car rest) (fluid define-bound-vars)))
(loop (cdr rest)
(cons (car rest) clauses)))))))
((letrec)
(let-fluids ((define-bound-vars
(nconc (mapcar (lambda (x) (or (car x) x)) (cadr form))
(fluid define-bound-vars))))
(list 'letrec
(mapcar (lambda (x)
(if (consp x)
(cons (car x) (define-scan-body (cdr x)))
x)) (cadr form))
(define-scan-internals (cddr form)))))
((let-fluids)
(list 'let-fluids
(mapcar (lambda (x)
(if (consp x)
(cons (car x) (define-scan-body (cdr x)))
x)) (cadr form))
(define-scan-internals (cddr form))))
((setq)
(let loop ((rest (cdr form))
(out nil))
(if rest
(loop (cddr rest)
(cons (list (car rest)
(define-scan-form (cadr rest))) out))
(cons (car form) (apply nconc (nreverse out))))))
((cond)
(cons 'cond (mapcar (lambda (clause)
(define-scan-body clause)) (cdr form))))
((case)
(list* 'case
(define-scan-form (nth 1 form))
(mapcar (lambda (clause)
(cons (car clause) (define-scan-body (cdr clause))))
(nthcdr 2 form))))
((condition-case)
(let ((var (if (eq (cadr form) 'nil) nil (cadr form))))
(let-fluids ((define-bound-vars (cons var (fluid define-bound-vars))))
(list* 'condition-case (cadr form)
(define-scan-body (cddr form))))))
((catch unwind-protect progn)
(cons (car form) (define-scan-body (cdr form))))
((quote structure-ref) form)
((lambda)
(let ((vars (let loop ((rest (cadr form))
(vars '()))
(cond ((null rest) vars)
((memq (or (caar rest) (car rest))
'(#!optional #!key #!rest &optional &rest))
(loop (cdr rest) vars))
(t (loop (cdr rest) (cons (or (caar rest)
(car rest)) vars))))))
(body (nthcdr 2 form))
(header nil))
;; skip doc strings and interactive decls..
(while (or (stringp (car body)) (eq (caar body) 'interactive))
(setq header (cons (car body) header))
(setq body (cdr body)))
`(lambda ,(cadr form)
,@(nreverse header)
,(let-fluids ((define-bound-vars
(nconc vars (fluid define-bound-vars))))
(define-scan-internals body)))))
((defvar)
(list* 'defvar (nth 1 form) (define-scan-form (nth 2 form))
(nthcdr 3 form)))
((structure define-structure declare) form)
(t (let ((expansion (define-macroexpand-1 form)))
(if (eq expansion form)
(define-scan-body form)
(define-scan-form expansion)))))))
;;;###autoload
(defmacro define (#!rest args)
(let ((def (define-parse args)))
(let ((var (car def))
(value (cadr def))
(doc (caddr def)))
(if (eq (car value) 'lambda)
`(defun ,var ,(cadr value)
,@(and doc (list doc))
,@(let ((body (cddr value)))
(if (and (eq (car body) 'progn) (null (cdr body)))
(cdar body)
body)))
(cons '%define def)))))
;;;###autoload
(defmacro define-macro (#!rest args)
(let ((def (define-parse args)))
(let ((var (car def))
(value (cadr def))
(doc (caddr def)))
(if (eq (car value) 'lambda)
`(defmacro ,var ,(cadr value)
,@(and doc (list doc))
,@(let ((body (cddr value)))
(if (and (eq (car body) 'progn) (null (cdr body)))
(cdar body)
body)))
;; can only expand to defmacro forms (for the compiler's sake)
(error "Macros must be constant lambdas: %s" (car def))))))
;;;###autoload
(defmacro with-internal-definitions (#!rest body)
(define-scan-internals body))
|
