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/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2009-2011, University of Amsterdam
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
:- module(portray_text,
[ portray_text/1, % +Bool
set_portray_text/2 % +Name, +Value
]).
:- use_module(library(error)).
/** <module> Portray text
A Prolog string is a list of character-codes: (small) integers, which
results in output like this:
==
?- writeln("hello").
[104, 101, 108, 108, 111]
==
Unless you know the Unicode tables by heart, this is pretty unpleasant
for debugging. Loading this library makes the toplevel and debugger
print strings with at least 3 characters as "text ...". Of course, this
is an ambigious operation because nobody can know whether [65,66] should
be written as "AB" or a list: to Prolog they are the same. Therefore it
is imported that the user is aware of the fact that this heuristic
conversion is enabled. This is why this library must be loaded
explicitely to enable this conversion.
@tbd Allow setting the character-codes we try to convert
*/
:- dynamic
do_portray_text/1,
portray_text_option/2.
do_portray_text(true).
portray_text_option(min_length, 3).
portray_text_option(ellipsis, 30).
%! portray_text(+Boolean) is det.
%
% If =true=, write lists of character codes as "..." to simplify
% debugging.
portray_text(OnOff) :-
must_be(boolean, OnOff),
retractall(do_portray_text(_)),
assert(do_portray_text(OnOff)).
%! set_portray_text(+Name, +Value) is det.
%
% Set options for writing lists as strings. Options are
%
% * min_length
% Only consider lists that are at least this long
% * ellipsis
% Write strings that are longer as "start...end"
set_portray_text(min_length, N) :-
must_be(nonneg, N),
retractall(portray_text_option(min_length, _)),
assert(portray_text_option(min_length, N)).
set_portray_text(ellipsis, N) :-
must_be(nonneg, N),
retractall(portray_text_option(ellipsis, _)),
assert(portray_text_option(ellipsis, N)).
:- multifile
user:portray/1.
:- dynamic
user:portray/1.
user:portray(Codes) :-
do_portray_text(true),
'$skip_list'(Length, Codes, Tail),
portray_text_option(min_length, MinLen),
Length >= MinLen,
all_ascii(Codes),
portray_text_option(ellipsis, IfLonger),
put_char('"'),
( Length > IfLonger
-> First is IfLonger - 5,
Skip is Length - 5,
skip_first(Skip, Codes, Rest),
put_n_codes(First, Codes),
format('...', [])
; Rest = Codes
),
( var_or_numbered(Tail)
-> put_var_codes(Rest)
; format('~s', [Rest])
),
put_char('"').
put_n_codes(N, [H|T]) :-
N > 0,
!,
emit_code(H),
N2 is N - 1,
put_n_codes(N2, T).
put_n_codes(_, _).
skip_first(N, [_|T0], T) :-
succ(N2, N),
!,
skip_first(N2, T0, T).
skip_first(_, L, L).
put_var_codes(Var) :-
var_or_numbered(Var),
!,
format('|~p', [Var]).
put_var_codes([]).
put_var_codes([H|T]) :-
emit_code(H),
put_var_codes(T).
emit_code(0'\b) :- !, format('\\b').
emit_code(0'\r) :- !, format('\\r').
emit_code(0'\n) :- !, format('\\n').
emit_code(0'\t) :- !, format('\\t').
emit_code(C) :- put_code(C).
all_ascii(Var) :-
var_or_numbered(Var),
!.
all_ascii([]).
all_ascii([H|T]) :-
isascii(H),
all_ascii(T).
isascii(Term) :-
integer(Term),
ascii_code(Term),
!.
ascii_code(9).
ascii_code(10).
ascii_code(13). % ok ...
ascii_code(C) :-
between(32, 126, C).
var_or_numbered(Var) :-
var(Var),
!.
var_or_numbered('$VAR'(_)).
|
