PicoJoy-in-Prolog
Martin Young in his message 9-AUG-2000 supplied a pointer,
http://www.endotether.clara.net/martin/joy
to his page on a version of Joy-in-Prolog. I have not yet had
the time to study it in depth, but it reminded me to dig out
an antique version of my own. It does not have a proper scanner
and lexer in the way Martin's has, and consequently it is
rather awful to use (see the short doc inside). I do have
a better scanner and parser which a friend wrote for me, and they
allow Joy lists to be written without the irritating commas in
Prolog lists. So they are a definite improvement, but
still do not quite live up to the "offical" Joy syntax. Moreover,
they are rather long, longer than this cut-down version, and so
I did not include them. I'll send them out if anyone wants them,
but as I said, Martin's solution to the syntax problem is probably
better.
I call this thing PicoJoy because it is a cut-down version
of what I used to call MicroJoy . Any experienced Prolog writer
should have no problem extending it. I hope Martin and perhaps
others can make use of it. It runs under MU-Prolog (from Melbourne
University), and probably under any other standard Prolog.
Manfred
/* file: picojoy.pl A tiniest Joy-in-Prolog */
/* Run Prolog, then "consult('picojoy.pl')." this file.
To enter the picojoy loop, type "picojoy." .
After the prompt, enter Joy programs
1) items separated by commas
2) program inside square bracket
3) program terminated by a period.
All this is inconvenient; it is necessary because picojoy
simply uses the prolog read/1 and write/1.
Two Examples: [3, 5, +]. [ [2,3,4], [dup,+], map ].
or Definition: [ foo, ==, bar, baz, zonk ].
Output is the whole stack.
To exit the loop, after the prompt type stop. (no brackets).
Now you are back in prolog. Typically end. or EOF exits.
*/
/* "outer interpreter" */
picojoy :-
write('picojoy version 00.00') ,
repeat,
nl,
write('j: ') ,
read(P) ,
( P == stop, !
;
P = [ HEAD,(==)|BODY ],
asserta((
exe(HEAD,(X,Y)) :-
exelist(BODY,(X,Y)) )),
fail
;
exelist(P , ([], Y)) ,
write(Y),
fail
) .
/* "inner interpreter" */
exelist([] , (X, X)) .
exelist(R1.R , (X, Z)) :-
exe(R1 , (X, Y)) ,
exelist(R , (Y, Z)) .
/* literals */
exe(true , (S, true.S)) .
exe(false , (S, false.S)) .
exe([] , (S, [].S)) .
exe(L1.L , (S, (L1.L).S)) .
exe(I , (S, I.S)) :-
integer(I) .
/* operators */
exe(stack , (S, S.S)) .
exe(unstack , (L.S, L)) .
exe(pop , (S1.S, S)) .
exe(dup , (S1.S, S1.S1.S)) .
exe(swap , (S1.S2.S, S2.S1.S)) .
exe(cons , (L.L1.S, (L1.L).S)) .
exe(null , ([].S, true.S)) :-
! .
exe(null , (X.S, false.S)) .
exe(uncons , ((L1.L).S, L.L1.S)) .
exe(unit , (S1.S, (S1.[]).S)) .
exe(pair , (S1.S2.S, (S2.S1.[]).S)) .
exe(unpair , ((L1.L2.L).S, L2.L1.S)) .
exe(concat , (L.[].S, L.S)) .
exe(concat , (L.(M1.M).S, (M1.N).S)) :-
exe(concat , (L.M.S, N.S)) .
exe(shunt , (L.[].S, L.S)) .
exe(shunt , (L.(M1.M).S, N.S)) :-
exe(shunt , ((M1.L).M.S, N.S)) .
exe(reverse , (L.S, M.S)) :-
exe(shunt , ([].L.S, M.S)) .
exe(size , ([].S, 0.S)) .
exe(size , ((L1.L).S, N.S)) :-
exe(size , (L.S, N1.S)) ,
N is N1 + 1 .
exe(+ , (X.Y.S, Z.S)) :-
Z is Y + X .
exe(= , (X.Y.S, true.S)) :-
Y = X .
exe(= , (X.Y.S, false.S)) :-
not (Y = X) .
exe(< , (X.Y.S, true.S)) :-
Y < X .
exe(< , (X.Y.S, false.S)) :-
not (Y < X) .
exe(first , ((L1.L).S, L1.S)) .
exe(second , ((L1.L2.L).S, L2.S)) .
exe(rest , ((L1.L).S, L.S)) .
/* combinators */
exe(i , (P.S, T)) :-
exelist(P , (S, T)) .
exe(dip , (P.S1.S, S1.T)) :-
exelist(P , (S, T)) .
exe(nullary , (P.S, X.S)) :-
exelist(P , (S, X.T)) .
exe(map , (P.[].S, [].S)) .
exe(map , (P.(L1.L).S, (M1.M).S)) :-
exelist(P , (L1.S, M1.T)) ,
exe(map , (P.L.S, M.U)) .
exe(step , (P.[].S, S)) .
exe(step , (P.(L1.L).S, U)) :-
exelist(P , (L1.S, T)) ,
exe(step , (P.L.T, U)) .
exe(sieve , (TEST.[].S, [].[].S)) .
exe(sieve , (TEST.(L1.L).S, N.(L1.M).S)) :-
exelist(TEST , (L1.S, true.T)) ,
!,
exe(sieve , (TEST.L.S, N.M.S)) .
exe(sieve , (TEST.(L1.L).S, (L1.N).M.S)) :-
exe(sieve , (TEST.L.S, N.M.S)) .
exe(filter , (TEST.[].S, [].S)) .
exe(filter , (TEST.(L1.L).S, (L1.M).S)) :-
exelist(TEST , (L1.S, true.T)) ,
!,
exe(filter , (TEST.L.S, M.S)) .
exe(filter , (TEST.(L1.L).S, M.S)) :-
exe(filter , (TEST.L.S, M.S)) .
exe(infra , (P.L.S, M.S)) :-
exelist(P , (L, M)) .
exe(ifte , (ELSEPART.THENPART.IFPART.S, T)) :-
exelist(IFPART , (S, true.U)) ,
!,
exelist(THENPART , (S, T)) .
exe(ifte , (ELSEPART.THENPART.IFPART.S, T)) :-
exelist(ELSEPART , (S, T)) .
exe(linrec , (REC2.REC1.EXIT.IF.S, T)) :-
exelist(IF , (S, true.U)) ,
!,
exelist(EXIT , (S, T)) .
exe(linrec , (REC2.REC1.EXIT.IF.S, T)) :-
exelist(REC1 , (S, U)) ,
exe(linrec , (REC2.REC1.EXIT.IF.U, V)) ,
exelist(REC2 , (V, T)) .
exe(listing, (S,S)) :- listing.
/* end of file picojoy.pl */