Opal (programming language)

OPAL (OPtimized Applicative Language) is a functional programming language first developed at the Technical University of Berlin.

Example program

This is an example OPAL program, which calculates the GCD recursively.
Signature file:

   SIGNATURE GCD
   FUN GCD: nat ** nat -> nat

Implementation file:

   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 (in German)