Availability:C-language interface function
predicate_t PL_predicate(const
char *name, int arity, const char* module)Same as PL_pred(),
but provides a more convenient interface to the C programmer. If the
module argument module is NULL
, the current
context module is used. The predicate_t
handle may be
stored as global data and reused for future queries227PL_predicate()
involves 5 hash lookups (two to get the atoms, one to get the module,
one to get the functor and the final one to get the predicate associated
with the functor in the module) as illustrated below.
static predicate_t p = 0;
...
if ( !p )
p = PL_predicate("is_a", 2, "database");
Note that PL_cleanup()
invalidates the predicate handle. Foreign libraries that use the above
mechanism must implement the module
uninstall() function to clear the predicate_t
global
variable.