60 lines
1.8 KiB
Prolog
60 lines
1.8 KiB
Prolog
/*
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Copyright 2019 Simon Forman
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This file is part of Thun
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Thun is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Thun is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Thun. If not see <http://www.gnu.org/licenses/>.
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DCG basics. For some of this I cribbed the source from SWI library code
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and adapted it for GNU Prolog Compiler.
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N.B. is_glyph//1 excludes '[' and ']' characters. D'oh! FIXME
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*/
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:- set_prolog_flag(double_quotes, codes).
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% TODO: scientific notation.
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signed_float_or_integer(Codes) --> signed_digits(J), ".", !, digits(I),
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{ append(J, [0'.|I], Codes) }.
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signed_float_or_integer(Codes) --> signed_digits(Codes).
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signed_digits([0'-|Codes]) --> "-", !, digits(Codes).
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signed_digits( Codes ) --> digits(Codes).
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% Groups of characters.
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chars(Chars) --> one_or_more(char, Chars).
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blanks --> blank, !, blanks | [].
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digits(Digits) --> one_or_more(digit, Digits).
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% Character types.
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char(Ch) --> [Ch], { nonvar(Ch), is_glyph(Ch) }.
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blank --> [Ch], { nonvar(Ch), is_space(Ch) }.
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digit(Ch) --> [Ch], { nonvar(Ch), between(0'0, 0'9, Ch) }.
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is_glyph(Ch) :- Ch =\= 0'[, Ch =\= 0'], between(0'!, 0'~, Ch).
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is_space(Ch) :- Ch =:= 32 ; between(9, 13, Ch).
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one_or_more(E, List) --> one_or_more_(List, E).
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one_or_more_([Ch|Rest], P) --> call(P, Ch), one_or_more_(Rest, P).
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one_or_more_([Ch], P) --> call(P, Ch).
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