query.

qid_t PL_current_query(void)

Returns the query id of the current query or 0 if the current thread is not executing any queries.

PL_engine_t PL_query_engine(qid_t qid)

Return the engine to which qid belongs. Note that interacting with a query or the Prolog terms associated with a query requires the engine to be current. See PL_set_engine().

int PL_call_predicate(module_t m, int flags, predicate_t pred, term_t +t0)

Shorthand for PL_open_query(), PL_next_solution(), PL_cut_query(), generating a single solution. The arguments are the same as for PL_open_query(), the return value is the same as PL_next_solution().

int PL_call(term_t t, module_t m)

Call term t just like the Prolog predicate once/1. t is called in the module m, or in the context module if m == NULL. Returns TRUE if the call succeeds, FALSE otherwise. If the goal raises an exception the return value is FALSE and the exception term is available using PL_exception(0).^{226Up to version 9.1.11 the debugger was started and the exception was not propagated.} Figure 7 shows an example to obtain the number of defined atoms.

12.4