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

Evaluates the expression Number1 "to the power of" Number2 and unifies the resulting value with Result.

Number1
  A number.
Number2
  A number.
Result
  Output: a number.

## 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 result is of type float if any of the arguments is a float. When an integer is raised to the power of a negative integer, the result type depends on the value of the global flag prefer_rationals. If it is on, it is a rational, otherwise a float. When the exponent is not an integer, the result is of type float.

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).
(24) number expected
  Number1 or Number2 is not of a numeric type.
(20) arithmetic exception
  Illegal arithmetic operation: Number1 is negative and Number2 is no integral number.
(20) arithmetic exception
  Illegal arithmetic operation: Number1 and Number2 are both zero.

## Examples

    Success:
        Result is 5 ^ 3.		% gives Result = 125
        Result is -5 ^ 3.		% gives Result = -125
        Result is 5 ^ -2.		% gives Result = 0.04

        Result is 5 ^ 2.2.		% gives Result = 34.493244
        Result is 5.0 ^ 2.		% gives Result = 25.0
        Result is -5.0 ^ 3.		% gives Result = -125.0
        Result is 0.0 ^ 12.3.	% gives Result = 0.0
        Result is 3.3 ^ 0.0.	% gives Result = 1.0
        Result is 0.0 ^ 0.0.	% gives Result = 1.0

    Error:
        Result is -5 ^ 0.5.         % arithmetic exception
        Result is -5.0 ^ 3.1.       % arithmetic exception

## See Also

is / 2, get_flag / 2, set_flag / 2