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 (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