[ Arithmetic | Reference Manual | Alphabetic Index ]
# ^(+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*
- A variable or 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:
^(5, 3, 125).
^(-5, 3, -125).
^(5, -2, 0.04).
^(5, 2.2, 34.493244).
^(5.0, 2, 25.0).
^(-5.0, 3, -125.0).
^(0.0, 12.3, 0.0).
^(3.3, 0.0, 1.0).
^(0.0, 0.0, 1.0).
Fail:
^(1, 2, 3).
^(1, 2, 3.0).
^(5, 2, r).
Error:
^(A, 2, 6). (Error 4).
^(-5, 0.5, X). (Error 20).
^(-5.0, 3.1, X). (Error 20).
^(2 + 3, 2, 25). (Error 24).

## See Also

is / 2, get_flag / 2, set_flag / 2