Fetching arguments of Prolog calls

Every C function that defines a Prolog predicate should not take any argument. The function bp_get_call_arg(i,arity) is used to get the arguments in the current Prolog call:

• TERM bp_get_call_arg(int i, int arity): Fetch the ith argument, where arity is the arity of the predicate, and i must be an integer between 1 and arity. The validness of the arguments are not checked and an invalid argument may cause fatal errors.