solution()">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. Figure 8 shows an example to obtain the number of defined atoms. All checks are omitted to improve readability.

12.4.11 Discarding Data

The Prolog data created and term references needed to set up the call and/or analyse the result can in most cases be discarded right after the call. PL_close_query() allows for destroying the data, while leaving the term references. The calls below may be used to destroy term references and data. See figure 8 for an example.

fid_t PL_open_foreign_frame()

Create a foreign frame, holding a mark that allows the system to undo bindings and destroy data created after it, as well as providing the environment for creating term references. This function is called by the kernel before calling a foreign predicate.

void PL_close_foreign_frame(fid_t id)

Discard all term references created after the frame was opened. All other Prolog data is retained. This function is called by the kernel whenever a foreign function returns control back to Prolog.

void PL_discard_foreign_frame(fid_t id)

Same as PL_close_foreign_frame(), but also undo all bindings made since the open and destroy all Prolog data.

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