Editing Gödel (programming language)

{{Infobox programming language
| name =Gödel
| logo =
| paradigm = [[Declarative programming|declarative]], [[Logic programming|logic]]
| year = 1992
| designer =John Lloyd & Patricia Hill
| developer = John Lloyd & Patricia Hill
| latest_release_version = 1.5
| latest release date ={{release date|1995|8|11}}
| typing = [[strong typing|strong]]
| implementations =
| dialects = [https://web.archive.org/web/20091207092823/http://www.scs.leeds.ac.uk/hill/GOEDEL/expgoedel.html Gödel with Generic (Parametrised) Modules]
| influenced_by =
| influenced =
| operating_system = [[Unix-like]]
| license = Non-commercial research/educational use only
| website = https://www.cs.unipr.it/~hill/GOEDEL/expgoedel.html
| file_ext =
}}

'''Gödel''' is a [[Declarative programming|declarative]], general-purpose [[programming language]] that adheres to the [[Logic programming|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]].

==Features==
Gödel has a module system, and it supports [[Arbitrary-precision arithmetic|arbitrary precision]] integers, arbitrary precision rationals, and also floating-point numbers. It can solve [[constraint (mathematics)|constraints]] over finite domains of integers and also linear rational constraints. It supports processing of [[finite set]]s. It also has a flexible computation rule and a pruning operator which generalises the commit of the concurrent logic programming languages.

Gödel's [[meta-logic]]al facilities provide support for meta-programs that do analysis, [[program transformation|transformation]], compilation, verification, and debugging, among other tasks.

==Sample code==

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 <code>CommonDivisor</code> predicate says that if <code>i</code> and <code>j</code> are not zero, then <code>d</code> is a common divisor of <code>i</code> and <code>j</code> if it lies between <code>1</code> and the smaller of <code>i</code> and <code>j</code> and divides both <code>i</code> and <code>j</code> exactly.
The <code>Gcd</code> predicate says that <code>d</code> is a greatest common divisor of <code>i</code> and <code>j</code> if it is a common divisor of <code>i</code> and <code>j</code>, and there is no <code>e</code> that is also a common divisor of <code>i</code> and <code>j</code> and is greater than <code>d</code>.

 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.

==External links==
* https://web.archive.org/web/20091207092823/http://www.scs.leeds.ac.uk/hill/GOEDEL/expgoedel.html
* https://mitpress.mit.edu/9780262519151/the-godel-programming-language/

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{{DEFAULTSORT:Godel (programming language)}}
[[Category:Logic programming languages|Godel]]
[[Category:Programming languages created in 1992]]
[[Category:Programming languages created by women]]