chrtest.pl

:- chr_constraint temp_persist/2, collect_persist/2, get_persist/2.

get_all_persistant(S, Persistant) :-
    chr_trace, chr_leash(-all),
    get_persist(S, Persistant).

persistant(S, Data), get_persist(S, _) ==> temp_persist(S, Data).
get_persist(S, Persist) <=> collect_persist(S, Persist).
temp_persist(S, Data), collect_persist(S, Persist) <=>
       Persist = [Data | Rest],
       collect_persist(S, Rest).
collect_persist(_, L) <=> L=[].

====================



:- use_module(library(chr)).

:- chr_constraint foo/1, get_foo/1, recurse_foo/1.

load_it :-
    foo(1),
    foo(3),
    foo(7).

% no backtrack get
foo(X) \ get_foo(Y) <=>
         X = Y.
get_foo(_) <=> fail.

/* doesnt work
foo(X), recurse_foo(Y) ==>
       Y = [ X | Rest  ],
       recurse_foo(Rest).
recurse_foo(_) <=> true.
*/

all_foos(L) :-
    nb_setval(all_foos_val, []),
    af(L).

af(_) :-
    find_chr_constraint(foo(X)),
    nb_getval(all_foos_val, OldL),
    nb_setval(all_foos_val, [X | OldL]),
    fail.
af(L) :-
    nb_getval(all_foos_val, L).

:- chr_constraint gather_foos_together/1, get_thy_foos/1.

foo(X) \ gather_foos_together(Old) <=> gather_foos_together([X | Old]).

gather_foos_together(Foos), get_thy_foos(Y) ==> Foos = Y.
% get_thy_foos(_) <=> true.   don't do this


:- chr_constraint get_foo_list/1.

foo(X), get_foo_list(L) ==>
          L=[X|L1], get_foo_list(L1).
get_foo_list(L) <=> L=[].


:- chr_constraint one_foo/1, collect_foo/1.

% copy constraints to be collected
foo(X), get_foo(_) ==> one_foo(X).
get_foo(L) <=> collect_foo(L).

% collect and remove copied constraints
one_foo(X), collect_foo(L) <=>
          L=[X|L1], collect_foo(L1).
collect_foo(L) <=> L=[].


Query with

?- halt.
anniepoo@anniesthinkpad:~/prologhelp$ swipl chrtest.pl
Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.0)
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software.
Please run ?- license. for legal details.

For online help and background, visit http://www.swi-prolog.org
For built-in help, use ?- help(Topic). or ?- apropos(Word).

?- edit.
true.

?- load_it, collect_foo(X).
X = [],
foo(7),
foo(3),
foo(1).

?-