[ 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
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
```