[ 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).

## See Also

is / 2