Registers the function, making it available to Rexx procedures. The module is the name of an external library where the native function is located. In some environments, such as Unix-like systems, the library name is case sensitive. The procedure is the name of the exported procedure inside of module. If procedure is not specified, it defaults to name. The procedure is generally case-sensitive. RxFuncAdd will attempt to resolve the procedure address using the name as specified and if that attempt fails, will retry using an uppercased name.

A return value 0 signifies successful registration and that the registered function has been located in the specified module. A return value 1 signifies that the function could not be resolved.

-- 0 if rxcalcsqrt can be located, else 1
rxfuncadd("rxcalcsqrt", "rxmath", "rxcalcsqrt")