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

Shifts Number1 left 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 if 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 *
- Number1 or Number2 is a number but not an integer.
*(24) number expected *
- Number1 or Number2 is not of a numeric type.

## Examples

Success:
<<(1, 3, 8).
Fail:
<<(1, 2, 3).
<<(6, 2.0, 24.0).
<<(5, 2, r).
Error:
<<(A, 2, 6). (Error 4).
<<(4 + 2, 2, 24). (Error 24).

## See Also

is / 2