Gödel (programming language)
|Designed by||John Lloyd & Patricia Hill|
|Developer||John Lloyd & Patricia Hill|
1.5 / August 11, 1995
|License||Non-commercial research/educational use only|
|Gödel with Generic (Parametrised) Modules|
Gödel is a declarative, general-purpose programming language that adheres to the logic programming paradigm. It is a strongly typed language, the type system being based on many-sorted logic with parametric polymorphism. It is named after logician Kurt Gödel.
Gödel has a module system, and it supports arbitrary precision integers, arbitrary precision rationals, and also floating-point numbers. It can solve constraints over finite domains of integers and also linear rational constraints. It supports processing of finite sets. 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.
CommonDivisor predicate says that if
j are not zero, then
d is a common divisor of
j if it lies between
1 and the smaller of
j and divides both
Gcd predicate says that
d is a greatest common divisor of
j if it is a common divisor of
j, and there is no
e that is also a common divisor of
j and is greater than
MODULE GCD. IMPORT Integers. PREDICATE Gcd : Integer * Integer * Integer. Gcd(i,j,d) <- CommonDivisor(i,j,d) & ~ SOME [e] (CommonDivisor(i,j,e) & e > d). PREDICATE CommonDivisor : Integer * Integer * Integer. CommonDivisor(i,j,d) <- IF (i = 0 \/ j = 0) THEN d = Max(Abs(i),Abs(j)) ELSE 1 =< d =< Min(Abs(i),Abs(j)) & i Mod d = 0 & j Mod d = 0.