create_constraint_pool(+PoolName, +NTypes, ++SpecList)

PoolName

Atom - the name of the pool to create

NTypes

Integer - the number of constraint types

SpecList

List of terms of the form Atom/Integer->Spec

Description

Create a special type of module, called a "constraint pool".

The module will contain:

• simple definitions for the predicates listed in SpecList. These definitions will just store or forward every call.
• a logical store which can be used to store and retrieve constraints, indexed by pool name and type. NTypes is the number of different constraint types that this pool will support.
• a logical store for one additional data item, for example a solver handle.

The possible specifications in SpecList are:

N/A -> store_as(Type)

will generate a definition for the predicate N/A such that every call to N/A will be stored in the pool for the given Type.

N/A -> ImplN/ImplA

will generate a definition for the predicate N/A such that every call to N/A gets augmented with an additional argument (the pool name), and mapped into a call to the implementation predicate ImplN/ImplA. The implementation predicate must be visible from where create_constraint_pool/3 is invoked. The implementation predicate's arity ImplA must be one higher than the the arity A of the newly defined predicate.

Since a pool is a module, the pool name should normally not refer to an existing module. If it does, the existing module gets augmented with the pool predicates and pool stores.

Examples

    % We assume the implementation predicate:
    d(Data, Pool) :- writeln(d(Data, Pool)).

    % Create the pool:
    ?- create_constraint_pool(pool, 1, [c/2->store_as(1),d/1->d/2]).
    Yes (0.00s cpu)

    % Call the just created pool constraint d/1,
    % which leads to d/2 being invoked:
    ?- pool:d(hello).
    d(hello, pool)
    Yes (0.00s cpu)

    % Call the just created pool constraint c/2,
    % which will be stored. Then retrieve the store:
    ?- pool:c(a,b), collect_all_pool_constraints(pool, C).
    C = [c(a, b)]
    Yes (0.00s cpu)
    

See Also