This is a draft, and incomplete, but I wanted to share it a little early.
Joy is a purely-functional, stack-based, "concatinative" language. Juxtaposition of names denotes composition of functions.
https://en.wikipedia.org/wiki/Joy_(programming_language)
http://www.kevinalbrecht.com/code/joy-mirror/joy.html
This mostly works, but there are some issues:
- I haven't implemented all the functions and combinators.
- It parses and passes numbers but the clp(fd) math only works with ints.
- The "compiler" doesn't work with loop or loop constructs (while).
Example evaluation:
?- joy(`0 [3 2 1] [+] step`, [], So).
So = [6] ;
false.
%
% Copyright © 2018 Simon Forman
%
% This file is part of Thun
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% Thun 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 3 of the License, or
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% Thun is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
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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
% along with Thun. If not see <
http://www.gnu.org/licenses/>.
%
:- use_module(library(clpfd)).
:- use_module(library(dcg/basics)).
:- op(990, xfy, ≡). % for Joy definitions.
/*
An entry point.
*/
joy(InputString, StackIn, StackOut) :-
phrase(joy_parse(Expression), InputString), !,
thun(Expression, StackIn, StackOut).
/*
Parser
*/
joy_parse([T|S]) --> blanks, joy_term(T), blanks, joy_parse(S).
joy_parse([]) --> [].
joy_term(N) --> number(N), !.
joy_term(S) --> "[", !, joy_parse(S), "]".
joy_term(A) --> chars(Chars), !, {atom_string(A, Chars)}.
chars([Ch|Rest]) --> char(Ch), chars(Rest).
chars([Ch]) --> char(Ch).
char(Ch) --> [Ch], {Ch \== 91, Ch \== 93, code_type(Ch, graph)}.
% Why not "]" or ']' or `]`? Why 93?
/*
Interpreter
thun(Expression, InputStack, OutputStack)
*/
thun([], S, S).
thun( [Lit|E], Si, So) :- literal(Lit), !, thun(E, [Lit|Si], So).
thun( [Func|E], Si, So) :- func(Func, Si, S), thun(E, S, So).
thun([Combo|E], Si, So) :- combo(Combo, Si, S, E, Eo), thun(Eo, S, So).
/*
Literals
*/
literal(V) :- var(V).
literal(I) :- number(I).
literal([]).
literal([_|_]).
literal(true).
literal(false).
/*
Functions
*/
func(app1, [P, Xi|S], [Xo|S]) :- thun(P, [Xi|S], [Xo|_]).
func(app2, [P, Xi, Yi|S], [Xo, Yo|S]) :- thun(P, [Xi|S], [Xo|_]), thun(P, [Yi|S], [Yo|_]).
func(cons, [A, B|S], [[B|A]|S]).
func(swap, [A, B|S], [B, A|S]).
func(dup, [A|S], [A, A|S]).
func(pop, [_|S], S ).
func(+, [A, B|S], [C|S]) :- C #= A + B.
func(-, [A, B|S], [C|S]) :- C #= B - A.
func(*, [A, B|S], [C|S]) :- C #= A * B.
func(/, [A, B|S], [C|S]) :- C #= B div A.
func(nullary, [P|S], [X|S]) :- thun(P, S, [X|_]). % Combinator.
func(infra, [P, R|S], [Q|S]) :- thun(P, R, Q). % Combinator.
func(concat, [A, B|S], [C|S]) :- append(B, A, C).
func(flatten, [A|S], [B|S]) :- flatten(A, B).
func(swaack, [R|S], [S|R]).
func(stack, S , [S|S]).
func(clear, _ , []).
func(first, [[X|_]|S], [X|S]).
func(rest, [[_|X]|S], [X|S]).
func(unit, [X|S], [[X]|S]).
func(rolldown, [A, B, C|S], [B, C, A|S]).
func(dupd, [A, B|S], [A, B, B|S]).
func(over, [A, B|S], [B, A, B|S]).
func(tuck, [A, B|S], [A, B, A|S]).
func(rollup, Si, So) :- func(rolldown, So, Si).
func(uncons, Si, So) :- func(cons, So, Si).
func(>, [A, B|S], [T|S]) :- B #> A #<==> R, r_truth(R, T).
func(<, [A, B|S], [T|S]) :- B #< A #<==> R, r_truth(R, T).
func(=, [A, B|S], [T|S]) :- B #= A #<==> R, r_truth(R, T).
func(>=, [A, B|S], [T|S]) :- B #>= A #<==> R, r_truth(R, T).
func(<=, [A, B|S], [T|S]) :- B #=< A #<==> R, r_truth(R, T).
func(<>, [A, B|S], [T|S]) :- B #\= A #<==> R, r_truth(R, T).
/*
Definitions
*/
func(Name, Si, So) :- Name ≡ Body, thun(Body, Si, So).
swons ≡ [swap, cons].
unswons ≡ [uncons, swap].
x ≡ [dup, i].
b ≡ [[i], dip, i].
sqr ≡ [dup, *].
ifte ≡ [[nullary], dipd, swap, branch].
while ≡ [swap, [nullary], cons, dup, dipd, concat, loop].
popop ≡ [pop, pop].
ccons ≡ [cons, cons].
unary ≡ [nullary, popd].
binary ≡ [unary, popd].
trinary ≡ [binary, popd].
popd ≡ [[pop], dip].
popdd ≡ [[pop], dipd].
popopd ≡ [[popop], dip].
popopdd ≡ [[popop], dipd].
dupd ≡ [[dup], dip].
dupdd ≡ [[dup], dipd].
second ≡ [rest, first].
third ≡ [rest, second].
fourth ≡ [rest, third].
rrest ≡ [rest, rest].
unit ≡ [[], cons].
drop ≡ [[rest], times].
at ≡ [drop, first].
of ≡ [swap, at].
sum ≡ [0, swap, [+], step].
product ≡ [1, swap, [*], step].
size ≡ [0, swap, [pop, 1, +], step].
fork ≡ [[i], app2].
cleave ≡ [fork, [popd], dip].
codireco ≡ [cons, dip, rest, cons].
make_generator ≡ [[codireco], ccons].
r_truth(0, false).
r_truth(1, true).
/*
Combinators
*/
combo(i, [P|S], S, Ei, Eo) :- append(P, Ei, Eo).
combo(dip, [P, X|S], S, Ei, Eo) :- append(P, [X|Ei], Eo).
combo(dipd, [P, X, Y|S], S, Ei, Eo) :- append(P, [Y, X|Ei], Eo).
combo(branch, [T, _, true|S], S, Ei, Eo) :- append(T, Ei, Eo).
combo(branch, [_, F, false|S], S, Ei, Eo) :- append(F, Ei, Eo).
combo(loop, [_, false|S], S, E, E ).
combo(loop, [B, true|S], S, Ei, Eo) :- append(B, [B, loop|Ei], Eo).
combo(step, [_, []|S], S, E, E ).
combo(step, [P, [X]|S], [X|S], Ei, Eo) :- !, append(P, Ei, Eo).
combo(step, [P, [X|Z]|S], [X|S], Ei, Eo) :- append(P, [Z, P, step|Ei], Eo).
combo(times, [_, 0|S], S, E, E ).
combo(times, [P, 1|S], S, Ei, Eo) :- append(P, Ei, Eo).
combo(times, [P, N|S], S, Ei, Eo) :- N #>= 2, M #= N - 1, append(P, [M, P, times|Ei], Eo).
combo(times, [_, N|S], S, _, _ ) :- N #< 0, fail.
/*
Compiler
*/
joy_compile(Name, Expression) :- jcmpl(Name, Expression, Rule), asserta(Rule).
show_joy_compile(Name, Expression) :- jcmpl(Name, Expression, Rule), write(Rule).
jcmpl(Name, Expression, Head :- Body) :-
call_residue_vars(thun(Expression, Si, So), Term),
copy_term(Term, Term, Gs),
Head =.. [func, Name, Si, So],
thrp(Gs, Body).
thrp([A,B], (A, B)) :- !.
thrp([A|B], (A, C)) :- thrp(B, C).
thrp([A], A).