_unify_bool(), but raises a type error if t is not a variable or a boolean.

The second family of functions in this section simplifies the generation of ISO compatible error terms. Any foreign function that calls this function must return to Prolog with the return code of the error function or the constant FALSE. If available, these error functions add the name of the calling predicate to the error context. See also PL_raise_exception().

int PL_instantiation_error(term_t culprit)

Raise instantiation_error. Culprit is ignored, but should be bound to the term that is insufficiently instantiated. See instantiation_error/1.

int PL_uninstantiation_error(term_t culprit)

Raise uninstantiation_error(culprit). This should be called if an argument that must be unbound at entry is bo