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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

### 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