[ Arithmetic | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]
# gcd(+Number1, +Number2, -Result)

Unifies Results with the Greatest Common Divisor of Number1 and Number2
*Number1*
- Integer.
*Number2*
- Integer.
*Result*
- A variable or integer.

## Description

This predicate is used by the ECLiPSe compiler to expand evaluable
arithmetic expressions. So the call to gcd(Number1, Number2, Result) is
equivalent to
Result is gcd(Number1, Number2)

which should be preferred for portability.
The Greatest Common Divisor operation is only defined on integer arguments.

In coroutining mode, if Number1 or Number2 are uninstantiated, the call
is delayed until these variables are instantiated.

### Modes and Determinism

### Exceptions

*(4) instantiation fault *
- Number1 or Number2 is not instantiated (non-coroutining mode only).
*(5) type error *
- Result is a number but not an integer.
*(5) type error *
- Number1 or Number2 is a number but not an integer.
*(24) number expected *
- Number1 or Number2 is not of a numeric type.
*(24) number expected *
- Result is neither a number nor a variable.

## Examples

Success:
gcd(9, 15, 3).
gcd(-9, 15, 3).
gcd(2358352782,97895234896224,X). ( gives X = 6 )
Error:
gcd(A, 2, 6). (Error 4).
gcd(1, 2, 3.0). (Error 5).
gcd(1.0, 2, 3.0). (Error 5).
gcd(4 + 2, 2, 12). (Error 24).

## See Also

lcm / 3, is / 2