Predicate references

This section discusses the functions used to communicate about predicates. Though a Prolog predicate may defined or not, redefined, etc., a Prolog predicate has a handle that is not destroyed, nor moved. This handle is known by the type predicate_t.

predicate_tPL_predfunctor_t f, module_t m Return a handle to a predicate for the specified name/arity in the given module. This function always succeeds, creating a handle for an undefined predicate if no handle was available. predicate_tPL_predicateconst char *name, int arity, const char* module Same a PL_pred, but provides a more convenient interface to the C-programmer. voidPL_predicate_infopredicate_t p, atom_t *n, int *a, module_t *m Return information on the predicate p. The name is stored over n, the arity over a, while m receives the definition module. Note that the latter need not be the same as specified with PL_predicate. If the predicate was imported into the module given to PL_predicate, this function will return the module where the predicate was defined.