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Function ^/2
Availability:Arithmetic function (see is/2)
[ISO]+Expr1 ^ +Expr2

In SWI-Prolog, ^/2 is equivalent to **/2. The ISO version is similar, except that it produces a evaluation error if both Expr1 and Expr2 are integers and the result is not an integer. The table below illustrates the behaviour of the exponentiation functions in ISO and SWI. Note that if the exponent is negative the behavior of Int^Int depends on the flag prefer_rationals, producing either a rational number or a floating point number.

Expr1 Expr2 FunctionSWIISO
IntInt**/2 Int or RationalFloat
IntFloat**/2 FloatFloat
RationalInt**/2 Rational-
FloatInt**/2 FloatFloat
FloatFloat**/2 FloatFloat
IntInt^/2 Int or RationalInt or error
IntFloat^/2 FloatFloat
RationalInt^/2 Rational-
FloatInt^/2 FloatFloat
FloatFloat^/2 FloatFloat
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LogicalCaptain said (2017-02-11T00:58:03):0 upvotes 0 0 downvotes
Picture of user LogicalCaptain.

Something weird

If SWI-Prolog has not been compiled with GMP, then ^/2 performs float operations:

?- X is 12^2.
X = 144.0.

?- X is 2^2.
X = 4.0.

And so does **/2

?- X is 12**2.
X = 144.0.

?- X is 2**2.
X = 4.0.

Do not confuse ^ exponention with the ^ exists operator

Outside of arithmetic contexts, the ^/2 operator is used to mark variables as "existentially quantified" (caret operator).

See this discussion:

[https://stackoverflow.com/questions/19931801/what-is-the-prolog-operator](What is the Prolog operator ^ (“caret”)?)

And this page:

bagof/3