The clpq and clpr libraries are ‘orphaned’, i.e., they
currently have no maintainer.
- Answers are projected onto a component, not onto a term
An answer is projected onto the variables the user wrote down, so it
does not mention the slack variables the solver uses internally. It can
still mention a variable that does not occur in the query, namely one
that a called predicate connected to the query variables by a
constraint.
copy_term/3
is projected the same way, onto the user-level variables of the
constraint store that is reachable from the copied term rather than onto
the term itself. It therefore reports constraints in which the copy
takes part, together with a fresh variable for each partner that was not
copied:
?- {X+Y>=1}, copy_term(X, C, Gs).
Gs = [{C+_>=1}],
{X+Y>=1}.
Use dump/3
to project onto a chosen list of variables. Here it says that
X by itself is unconstrained:
?- {X+Y>=1}, dump([X], [x], L).
L = [],
{X+Y>=1}.
- Dumping constraints
The first argument of dump/3
has to be a list of free variables at call-time:
?- {X=1}, dump([X],[Y],L).
ERROR: Uninstantiated argument expected, found 1
