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

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

Shifts Number1 right arithmetically by Number2 bits 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.

The shift behaves as an arithmetic (signed) shift operating on an unlimited length two's complement representation. Shifting by a negative amount is the same as shifting by the same positive amount in the other direction.

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
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:
>>(8, 3, 1).
>>(17, 3, X).          (gives X = 2)
Fail:
>>(1, 2, 3).
Error:
>>(A, 2, 6).              (Error 4).
>>(16, 2.0, 4.0).         (Error 5).
>>(4 + 12, 2, 4).         (Error 24).
>>(5, 2, r).              (Error 24).

```