[ 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

### 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).

## See Also

is / 2