It also has a flexible computation rule and a pruning operator which generalises the commit of the concurrent logic programming languages.
Gödel's meta-logical facilities provide support for meta-programs that do analysis, transformation, compilation, verification, and debugging, among other tasks.
The following Gödel module is a specification of the greatest common divisor (GCD) of two numbers.
It is intended to demonstrate the declarative nature of Gödel, not to be particularly efficient.
The CommonDivisor predicate says that if i and j are not zero, then d is a common divisor of i and j if it lies between 1 and the smaller of i and j and divides both i and j exactly.