OPAL (OPtimized Applicative Language) is a

functional programming language In computer science, functional programming is a programming paradigm where programs are constructed by applying and composing functions. It is a declarative programming paradigm in which function definitions are trees of expressions that ...

first developed at the Technical University of Berlin.

Example program

This is an example OPAL program, which calculates the GCD recursively. ; Signature file (declaration) SIGNATURE GCD FUN GCD: nat ** nat -> nat ; Implementation file (definition) IMPLEMENTATION GCD IMPORT Nat COMPLETELY DEF GCD(a,b)

IF a % b = 0 THEN b ELSE IF a-b < b THEN GCD(b,a-b) ELSE GCD(a-b,b) FI FI

External links

The OPAL Home Page

OPAL Installation Guide
Functional languages {{compu-lang-stub