====== Comon divisor ======
{{tag>math}}
===== Description =====
Computing the greatest common divisor of two integers.

**Source**:  The Art of Prolog
===== Download =====
Program source code: {{comon_divisor.pl}}
===== Listing =====
<code prolog>
/*
   greatest_common_divisor(X,Y,Z) :- 
	Z is the greatest common divisor of the integers X and Y.
*/
     greatest_common_divisor(I,0,I).
     greatest_common_divisor(I,J,Gcd) :-
          J > 0, R is I mod J, greatest_common_divisor(J,R,Gcd).

%  Program 8.1    Computing the greatest common divisor of two integers
</code>
===== Comments =====