[ Arithmetic | The ECLiPSe Built-In Predicates | 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

- ^(+, +, -) is det

### Exceptions

(4) instantiation fault
  Number1 or Number2 is not instantiated (non-coroutining mode only).
(5) type error
  Result is of a different type than the evaluation result.
(24) number expected
  Number1 or Number2 is not of a numeric type.
(24) number expected
  Result is neither a number nor a variable.
(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).
    Fail:
          ^(1, 2, 3).
    Error:
          ^(A, 2, 6).             (Error 4).
          ^(1, 2, 3.0).           (Error 5).
          ^(-5, 0.5, X).          (Error 20).
          ^(2 + 3, 2, 25).        (Error 24).
          ^(5, 2, r).             (Error 24).

## See Also

is / 2, get_flag / 2, set_flag / 2