
chr_get_constraint(?Constraint)

   Remove a constraint unifying with Constraint from the constraint store.



Arguments
   ?Constraint         A constraint (callable term) defined by constraint handling                rules.

Type
   library(chr)

Description
   Removes a constraint unifying with Constraint from the constraint store.
   Note that if the unification with Constraint binds variables occurring
   also in other constraints in the constraint store, these constraints may
   be simplified (see last examples).  Thus it is recommended to use either
   a free variable or a term with variable arguments for Constraint.  Used
   by advanced constraint handling rules users to manipulate themselves the
   constraints defined by constraint handling rules.




Fail Conditions
      Fails if there is no constraint (defined by constraint handling rules)
   in the constraint store that unifies with Constraint.



Resatisfiable
      Yes.

Examples
      Example using the constraint handler for Booleans  bool.chr:
[eclipse]: chr_get_constraint(C).
no (more) solution.

[eclipse]: and(X,Y,Z), or(X,Y,Z).

Constraints:
(1) X_g745 * Y_g777 = Z_g809 % pretty print of and/3 constraint
(2) X_g745 + Y_g777 = Z_g809 % pretty print of or/3 constraint

yes.

[eclipse]: and(X,Y,Z), or(X,Y,Z), chr_get_constraint(C).

C = X * Y = Z

Constraints:
(2) X_g765 + Y_g797 = Z_g829
     More? (;)

C = X + Y = Z

Constraints:
(1) X_g765 * Y_g797 = Z_g829
     More? (;)
no (more) solution.

[eclipse]: and(X,Y,Z), or(X,Y,Z), chr_get_constraint(and(1,A,B)).
% or/3 - constraint is solved when X is bound to 1
X = 1
Y = A
Z = 1
A = A
B = 1

[eclipse]: and(X,Y,Z), or(X,Y,Z), chr_get_constraint(and(1,1,0)).
no (more) solution. % or/3 - constraint fails

[eclipse]: and(X,Y,Z), chr_get_constraint(and(1,1,0)).

X = 1
Y = 1
Z = 0


   The predicate chr_labeling/0 can be defined as:
labeling :-
   chr_get_constraint(C),
   chr_label_with(C),
   !,
   chr_resolve(C),
   labeling.

labeling.





See Also
   chr_labeling / 0, chr_label_with / 1, chr_resolve / 1, chr_get_constraint / 1, chr_get_constraint / 2
