418 lines
13 KiB
Prolog
418 lines
13 KiB
Prolog
%
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% Copyright © 2018, 2019, 2020 Simon Forman
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%
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% This file is part of Thun
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%
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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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%
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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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%
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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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%
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:- use_module(library(clpfd)).
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:- use_module(library(dcg/basics)).
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:- dynamic func/3.
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:- dynamic def/2.
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/*
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To handle comparision operators the possibility of exceptions due to
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insufficiently instantiated arguments must be handled. First try to make
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the comparison and set the result to a Boolean atom. If an exception
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happens just leave the comparison expression as the result and some other
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function or combinator will deal with it. Example:
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func(>, [A, B|S], [C|S]) :- catch(
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(B > A -> C=true ; C=false),
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_,
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C=(B>A) % in case of error.
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).
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To save on conceptual overhead I've defined a term_expansion/2 that sets
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up the func/3 for each op.
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*/
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term_expansion(comparison_operator(X), (func(X, [A, B|S], [C|S]) :-
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F =.. [X, B, A], catch((F -> C=true ; C=false), _, C=F))).
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% I don't use Prolog-compatible op symbols in all cases.
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term_expansion(comparison_operator(X, Y), (func(X, [A, B|S], [C|S]) :-
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F =.. [Y, B, A], catch((F -> C=true ; C=false), _, C=F))).
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% Likewise for math operators, try to evaluate, otherwise use the
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% symbolic form.
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term_expansion(math_operator(X), (func(X, [A, B|S], [C|S]) :-
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F =.. [X, B, A], catch(C is F, _, C=F))).
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term_expansion(math_operator(X, Y), (func(X, [A, B|S], [C|S]) :-
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F =.. [Y, B, A], catch(C is F, _, C=F))).
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/*
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An entry point.
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*/
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joy(InputString, StackIn, StackOut) :-
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phrase(joy_parse(Expression), InputString), !,
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thun(Expression, StackIn, StackOut).
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/*
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Parser
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The grammar of Joy is very simple. A Joy expression is zero or more Joy
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terms separated by blanks and terms can be either integers, quoted Joy
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expressions, or symbols (names of functions.)
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joy ::= ( blanks term blanks )*
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term ::= integer | '[' joy ']' | symbol
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integer ::= [ '-' | '+' ] ('0'...'9')+
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symbol ::= char+
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char ::= <Any non-space other than '[' and ']'.>
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blanks ::= <Zero or more whitespace characters.>
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For integer//1 and blanks//0 I delegate to SWI's dcg/basics library. The
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blank//0 matches and discards space and newline characters and integer//1
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"processes an optional sign followed by a non-empty sequence of digits
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into an integer." (https://www.swi-prolog.org/pldoc/man?section=basics)
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Symbols can be made of any non-blank characters except '['and ']' which
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are fully reserved for list literals ("quotes"), and '==' is reserved as
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a kind of meta-logical punctuation for definitions (it's not a symbol,
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you can't use it in code, it only appears in the defs.txt file as a
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visual aid to humans. The rule of one definition per line with the
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name as the first symbol in the definition would suffice, but I tried it
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and it looked ugly to me. Any number of '=' characters can appear as
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part of a symbol, and any number of them other than two can be a symbol.)
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Symbols 'true' and 'false' are treated as literals for Boolean values.
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For now strings are neglected in favor of lists of numbers. (But there's
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no support for parsing string notation and converting to lists of ints.)
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One wrinkle of the grammar is that numbers do not need to be followed by
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blanks before the next match, which is nice when the next match is a
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square bracket but a little weird when it's a symbol term. E.g. "2[3]"
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parses as [2, [3]] but "23x" parses as [23, x]. It's a minor thing not
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worth disfiguring the grammar to change IMO.
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Integers are converted to Prolog integers, symbols to Prolog atoms, and
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list literals to Prolog lists.
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*/
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joy_parse([T|J]) --> blanks, joy_term(T), blanks, joy_parse(J).
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joy_parse([]) --> [].
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joy_term(J) --> integer(J) | "[", joy_parse(J), "]" | symbol(J).
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symbol(C) --> chars(Chars), {Chars \= `==`, atom_string(C, Chars)}.
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chars([Ch|Rest]) --> char(Ch), chars(Rest).
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chars([Ch]) --> char(Ch).
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char(Ch) --> [Ch], {Ch \== 91, Ch \== 93, code_type(Ch, graph)}.
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/*
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Interpreter
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thun(Expression, InputStack, OutputStack)
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*/
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thun([], S, S).
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thun( [Lit|E], Si, So) :- literal(Lit), !, thun(E, [Lit|Si], So).
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thun( [Def|E], Si, So) :- def(Def, Body), !, append(Body, E, Eo), thun(Eo, Si, So).
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thun( [Func|E], Si, So) :- func(Func, Si, S), thun(E, S, So).
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thun([Combo|E], Si, So) :- combo(Combo, Si, S, E, Eo), thun(Eo, S, So).
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% Some error handling.
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thun([Unknown|E], Si, So) :-
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damned_thing(Unknown),
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write("wtf? "),
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writeln(Unknown),
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So = [Unknown|E]-Si.
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damned_thing(It) :-
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\+ literal(It),
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\+ def(It, _),
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\+ func(It, _, _),
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\+ combo(It, _, _, _, _).
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/*
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Literals
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*/
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literal(V) :- var(V).
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literal(I) :- number(I).
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literal([]).
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literal([_|_]).
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literal(true).
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literal(false).
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% Symbolic math expressions are literals.
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literal(_+_).
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literal(_-_).
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literal(_*_).
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literal(_/_).
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literal(_ mod _).
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% Symbolic comparisons are literals.
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literal(_>_).
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literal(_<_).
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literal(_>=_).
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literal(_=<_).
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literal(_=:=_).
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literal(_=\=_).
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/*
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Functions
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*/
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func(words, S, [Words|S]) :- words(Words).
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func(cons, [A, B|S], [[B|A]|S]).
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func(swap, [A, B|S], [B, A|S]).
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func(dup, [A|S], [A, A|S]).
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func(pop, [_|S], S ).
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% Symbolic math. Compute the answer, or derivative, or whatever, later.
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math_operator(+).
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math_operator(-).
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math_operator(*).
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math_operator(/).
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math_operator(mod).
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% Attempt to calculate the value of a symbolic math expression.
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func(calc, [A|S], [B|S]) :- B is A.
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func(sqrt, [A|S], [sqrt(A)|S]).
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func(concat, [A, B|S], [C|S]) :- append(B, A, C).
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func(flatten, [A|S], [B|S]) :- flatten(A, B).
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func(swaack, [R|S], [S|R]).
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func(stack, S , [S|S]).
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func(clear, _ , []).
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func(first, [[X|_]|S], [X|S]).
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func(rest, [[_|X]|S], [X|S]).
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func(unit, [X|S], [[X]|S]).
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func(rolldown, [A, B, C|S], [B, C, A|S]).
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func(dupd, [A, B|S], [A, B, B|S]).
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func(over, [A, B|S], [B, A, B|S]).
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func(tuck, [A, B|S], [A, B, A|S]).
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func(shift, [[B|A], C|D], [A, [B|C]|D]).
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func(rollup, Si, So) :- func(rolldown, So, Si).
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func(uncons, Si, So) :- func(cons, So, Si).
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func(bool, [ 0|S], [false|S]) :- !.
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func(bool, [ 0.0|S], [false|S]) :- !.
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func(bool, [ []|S], [false|S]) :- !.
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func(bool, [ ""|S], [false|S]) :- !.
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func(bool, [false|S], [false|S]) :- !.
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func(bool, [_|S], [true|S]).
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comparison_operator(>).
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comparison_operator(<).
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comparison_operator(>=).
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comparison_operator(<=, =<).
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comparison_operator(=, =:=).
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comparison_operator(<>, =\=).
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/*
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Combinators
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*/
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combo(i, [P|S], S, Ei, Eo) :- append(P, Ei, Eo).
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combo(dip, [P, X|S], S, Ei, Eo) :- append(P, [X|Ei], Eo).
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combo(dipd, [P, X, Y|S], S, Ei, Eo) :- append(P, [Y, X|Ei], Eo).
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combo(dupdip, [P, X|S], [X|S], Ei, Eo) :- append(P, [X|Ei], Eo).
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combo(branch, [T, _, true|S], S, Ei, Eo) :- append(T, Ei, Eo).
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combo(branch, [_, F, false|S], S, Ei, Eo) :- append(F, Ei, Eo).
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combo(branch, [T, F, Expr|S], S, Ei, Eo) :-
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\+ Expr = true, \+ Expr = false,
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catch( % Try Expr and do one or the other,
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(Expr -> append(T, Ei, Eo) ; append(F, Ei, Eo)),
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_, % If Expr don't grok, try both branches.
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(append(T, Ei, Eo) ; append(F, Ei, Eo))
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).
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combo(loop, [_, false|S], S, E, E ).
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combo(loop, [B, true|S], S, Ei, Eo) :- append(B, [B, loop|Ei], Eo).
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combo(loop, [B, Expr|S], S, Ei, Eo) :-
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\+ Expr = true, \+ Expr = false,
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catch( % Try Expr and do one or the other,
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(Expr -> append(B, [B, loop|Ei], Eo) ; Ei=Eo),
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_, % If Expr don't grok, try both branches.
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(Ei=Eo ; append(B, [B, loop|Ei], Eo))
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).
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combo(step, [_, []|S], S, E, E ).
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combo(step, [P, [X]|S], [X|S], Ei, Eo) :- !, append(P, Ei, Eo).
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combo(step, [P, [X|Z]|S], [X|S], Ei, Eo) :- append(P, [Z, P, step|Ei], Eo).
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combo(times, [_, 0|S], S, E, E ).
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combo(times, [P, 1|S], S, Ei, Eo) :- append(P, Ei, Eo).
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combo(times, [P, N|S], S, Ei, Eo) :- N #>= 2, M #= N - 1, append(P, [M, P, times|Ei], Eo).
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combo(times, [_, N|S], S, _, _ ) :- N #< 0, fail.
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combo(genrec, [R1, R0, Then, If|S],
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[ Else, Then, If|S], E, [ifte|E]) :-
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Quoted = [If, Then, R0, R1, genrec],
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append(R0, [Quoted|R1], Else).
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/*
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This is a crude but servicable implementation of the map combinator.
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Obviously it would be nice to take advantage of the implied parallelism.
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Instead the quoted program, stack, and terms in the input list are
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transformed to simple Joy expressions that run the quoted program on
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prepared copies of the stack that each have one of the input terms on
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top. These expressions are collected in a list and the whole thing is
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evaluated (with infra) on an empty list, which becomes the output list.
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The chief advantage of doing it this way (as opposed to using Prolog's
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map) is that the whole state remains in the pending expression, so
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there's nothing stashed in Prolog's call stack. This preserves the nice
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property that you can interrupt the Joy evaluation and save or transmit
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the stack+expression knowing that you have all the state.
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*/
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combo(map, [_, []|S], [[]|S], E, E ) :- !.
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combo(map, [P, List|S], [Mapped, []|S], E, [infra|E]) :-
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prepare_mapping(P, S, List, Mapped).
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% Set up a program for each term in ListIn
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%
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% [term S] [P] infrst
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%
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% prepare_mapping(P, S, ListIn, ListOut).
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prepare_mapping(P, S, In, Out) :- prepare_mapping(P, S, In, [], Out).
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prepare_mapping( _, _, [], Out, Out) :- !.
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prepare_mapping( P, S, [T|In], Acc, Out) :-
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prepare_mapping(P, S, In, [[T|S], P, infrst|Acc], Out).
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/*
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Definitions
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*/
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joy_def(def(Def, Body)) --> symbol(Def), blanks, "==", joy_parse(Body).
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joy_def --> joy_def(Def), {ignore(assert_def(Def))}.
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joy_defs --> blanks, joy_def, blanks, joy_defs.
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joy_defs --> [].
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assert_defs(DefsFile) :-
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read_file_to_codes(DefsFile, Codes, []),
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phrase(joy_defs, Codes).
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assert_def(def(Def, Body)) :-
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\+ func(Def, _, _),
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\+ combo(Def, _, _, _, _),
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retractall(def(Def, _)),
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assertz(def(Def, Body)).
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:- assert_defs("defs.txt").
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words(Words) :-
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findall(Name, clause(func(Name, _, _), _), Funcs),
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findall(Name, clause(combo(Name, _, _, _, _), _), Combos, Funcs),
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findall(Name, clause(def(Name, _), _), Words0, Combos),
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list_to_set(Words0, Words1),
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sort(Words1, Words).
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/*
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Compiler
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*/
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joy_compile(Name, Expression) :- jcmpl(Name, Expression, Rule), asserta(Rule).
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show_joy_compile(Name, Expression) :- jcmpl(Name, Expression, Rule), portray_clause(Rule).
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jcmpl(Name, Expression, Rule) :-
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call_residue_vars(thun(Expression, Si, So), Term),
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copy_term(Term, Term, Gs),
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Head =.. [func, Name, Si, So],
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rule(Head, Gs, Rule).
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rule(Head, [], Head ).
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rule(Head, [A|B], Head :- maplist(call, [A|B])).
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sjc(Name, InputString) :- phrase(joy_parse(E), InputString), show_joy_compile(Name, E).
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% Simple DCGs to expand/contract definitions.
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expando, Body --> [Def], {def(Def, Body)}.
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contracto, [Def] --> {def(Def, Body)}, Body.
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% Apply expando/contracto more than once, and descend into sub-lists.
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% The K term is one of expando or contracto, and the J term is used
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% on sub-lists, i.e. expando/grow and contracto/shrink.
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% BTW, "rebo" is a meaningless name, don't break your brain
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% trying to figure it out.
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rebo(K, J) --> K , rebo(K, J).
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rebo(K, J), [E] --> [[H|T]], !, {call(J, [H|T], E)}, rebo(K, J).
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rebo(K, J), [A] --> [ A ], !, rebo(K, J).
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rebo(_, _) --> [].
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to_fixed_point(DCG, Ei, Eo) :-
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phrase(DCG, Ei, E), % Apply DCG...
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(Ei=E -> Eo=E ; to_fixed_point(DCG, E, Eo)). % ...until a fixed-point is reached.
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grow --> to_fixed_point(rebo(expando, grow )).
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shrink --> to_fixed_point(rebo(contracto, shrink)).
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% ?- phrase(grow, [third], Out).
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% Out = [rest, rest, first] ;
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% Out = [rest, rest, first] ;
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% Out = [rest, second] ;
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% Out = [third].
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% ?- phrase(grow, In, [rest, rest, first]).
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% Action (h for help) ? abort
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% % Execution Aborted
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% ?- phrase(shrink, [rest, rest, first], Out).
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% Out = [rrest, first] ;
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% Out = [third] ;
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% Out = [rest, second] ;
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% Out = [rest, rest, first].
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% format_n(N) --> {number(N), !, number_codes(N, Codes)}, Codes.
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% format_n(N) --> signed_digits(Codes), !, {number_codes(N, Codes)}.
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% signed_digits([45|Codes]) --> [45], !, digits(Codes).
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% signed_digits( Codes ) --> digits(Codes).
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% digits([Ch|Chars]) --> [Ch], {code_type(Ch, digit)}, digits(Chars).
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% digits([]), [Ch] --> [Ch], {code_type(Ch, space) ; Ch=0'] }.
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% digits([], [], _). % Match if followed by space, ], or nothing.
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