[ 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 free variables, the call to ^/3 is delayed until these variables are instantiated.

Fail Conditions

Fails if the result of the evaluation does not unify with Result.

Resatisfiable

No

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