[ Arithmetic | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]

# //(+Number1, +Number2, -Result)

Evaluates the integer quotient Number1 // Number2 and unifies the resulting value with Result.
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 //(Number1, Number2, Result) is equivalent to
```    Result is Number1 // Number2
```
which should be preferred for portability.

This division operates on integer arguments, and delivers an integer result rounded towards zero (truncated). The corresponding remainder is computed by the rem operation, such that the following equivalence always holds:

```    X =:= (X rem Y) + (X // Y) * Y.
```

In coroutining mode, if Number1 or Number2 are uninstantiated, the call to (//)/3 is delayed until these variables are instantiated.

### Modes and Determinism

• //(+, +, -) is det

### Exceptions

(4) instantiation fault
Number1 or Number2 is not instantiated (non-coroutining mode only).
(5) type error
Number1 or Number2 is a number but not an integer.
(5) type error
Result 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.
(20) arithmetic exception
Illegal arithmetic operation: division by 0

## Examples

```Success:
X is 10 // 3.		( gives X = 3)

//( 10,  3,  3).
//(-10,  3, -3).
//( 10, -3, -3).
//(-10, -3,  3).

Fail:
//(1, 2, 3).
Error:
//(A, 2, 6).              (Error 4).
//(5, 2, r).              (Error 5).
//(6, 2.0, 3.0).          (Error 5).
//(2, 0, Result).        (Error 20).
//(4 + 2, 2, 12).        (Error 24).
```