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Update custom constraint example #24

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Update custom constraint example #24

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f4e88fa
Update custom constraint example
jeshan Oct 22, 2023
1360cbf
Update clpz.pl
jeshan Oct 23, 2023
a70cdab
add braces in multifile declaration and update comment
jeshan Oct 23, 2023
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36 changes: 24 additions & 12 deletions clpz.pl
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Original file line number Diff line number Diff line change
Expand Up @@ -938,19 +938,30 @@
one of X and Y is instantiated:

==
:- multifile clpz:run_propagator/2.
:- multifile(clpz:run_propagator/4).

oneground(X, Y, Z) :-
clpz:make_propagator(oneground(X, Y, Z), Prop),
clpz:init_propagator(X, Prop),
clpz:init_propagator(Y, Prop),
clpz:trigger_once(Prop).

clpz:run_propagator(oneground(X, Y, Z), MState) :-
( integer(X) -> clpz:kill(MState), Z = 1
; integer(Y) -> clpz:kill(MState), Z = 1
; true
).
clpz:make_propagator(oneground(X,Y,Z), Prop),
clpz:init_propagator(X, Prop),
clpz:init_propagator(Y, Prop),
clpz:trigger_once(Prop).

clpz:run_propagator(oneground(X,Y,Z), MState) -->
{
(
integer(X)
->
clpz:kill(MState),
Z = 1
; (
integer(Y)
->
clpz:kill(MState),
Z = 1
; true
)
)
}.
==

First, clpz:make_propagator/2 is used to transform a user-defined
Expand All @@ -959,7 +970,7 @@
Y. From now on, the propagator will be invoked whenever the domains of
X or Y are changed. Then, clpz:trigger_once/1 is used to give the
propagator its first chance for propagation even though the variables'
domains have not yet changed. Finally, clpz:run_propagator/2 is
domains have not yet changed. Finally, clpz:run_propagator//2 is
extended to define the actual propagator. As explained, this predicate
is automatically called by the constraint solver. The first argument
is the user-defined representation of the constraint as used in
Expand Down Expand Up @@ -4328,6 +4339,7 @@

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

:- multifile(clpz:run_propagator/4).
%run_propagator(P, _) --> { portray_clause(run_propagator(P)), false }.
% trivial propagator, used only to remember pending constraints
run_propagator(presidual(_), _) --> [].
Expand Down