C.7 Creating External Predicates in C
This function serves the same purpose as the ECLiPSe built-in external/2:
int ec_external(dident pred, int(*fct)(), dident module)
Creates a predicate pred in the given module, whose C/C++
implementation is the function fct (see chapter 4
for how to write such functions). The module must exist.
Return code is PSUCCEED or an error code.