Examples
?- X is 2 ** 1.
X = 2
yes
?- X is 2 ** 2.
X = 4
yes
?- X is 2 ** 5.
X = 32
yes
?- X is 5 ** 3.
X = 125
yes
?- X is 5.0 ** 3.
X = 125.0
yes
?- X is 5 ** 3.0.
X = 125.0
yes
?- X is 5.0 ** 3.0.
X = 125.0
yes
?- X is 2 + 5 ** 3 - 1.
X = 126
yes
?- X is -2 ** 2.
X = 4
yes
?- X is -2 ** -2.
X = 0.25
yes
?- X is 2 ** -2.
X = 0.25
yes
?- X is 0.5 ** 2.
X = 0.25
yes
?- X is 2 ** 3.
X = 8
yes
?- X is 2 ** -3.
X = 0.125
yes
?- X is 1 ** -100.
X = 1
yes
?- X is -1 ** -3.
X = -1
yes
?- X is 0 ** 2.
X = 0
yes
?- X is 2 ** 0.25.
X = 1.189207115002721
yes
?- X is 2 ** -0.25.
X = 0.8408964152537145
yes
?- X is -2 ** 0.25.
X = NaN
yes
?- X is -2 ** -0.25.
X = NaN
yes
?- X is 0 ** -1.
X = Infinity
yes
?- X is 0.0 ** -1.0.
X = Infinity
yes
?- X is 0 ** 0.
X = 1
yes
?- X is 0.0 ** 0.0.
X = 1.0
yes
?- X is 1 ** -5.
X = 1
yes
?- X is -1 ** -4.
X = 1
yes
?- X is -1 ** -5.
X = -1
yesNote: "^" is a synonym for "**".
?- X is 3^7.
X = 2187
yes