powr

Compute the value of x raised to the power of y, where x ≥ 0.

Interface Definition

C interface:

float powrf(float x, float y);

double powr(double x, double y);

Parameters

Parameter	Type	Description	Input/Output
x	For powrf, x is of single-precision floating-point type. For powr, x is of double-precision floating-point type.	Floating-point value of the input data.	Input
y	For powrf, y is of single-precision floating-point type. For powr, y is of double-precision floating-point type.	Floating-point value of the input data.	Input

Return Value

If x is greater than or equal to 0 and y is not a special value, the result of x raised to the power of y is returned. Value range: (0, +INF)
If x is less than 0, the return value is NaN.

Other combinations of special values are listed in the following table.

Input Value (x)	Input Value (y)	Output Value (result)
+0	+0	+1
+0	-0	+1
+0	inf	+0
+0	-inf	inf
+0	snan	nan
+0	-snan	nan
+0	qnan	nan
+0	-qnan	nan
-0	+0	+1
-0	-0	+1
-0	inf	+0
-0	-inf	inf
-0	snan	nan
-0	-snan	nan
-0	qnan	nan
-0	-qnan	nan
inf	+0	+1
inf	-0	+1
inf	inf	inf
inf	-inf	+0
inf	snan	nan
inf	-snan	nan
inf	qnan	nan
inf	-qnan	nan
-inf	+0	nan
-inf	-0	nan
-inf	inf	nan
-inf	-inf	nan
-inf	snan	nan
-inf	-snan	nan
-inf	qnan	nan
-inf	-qnan	nan
snan	+0	+1
snan	-0	+1
snan	inf	nan
snan	-inf	nan
snan	snan	nan
snan	-snan	nan
snan	qnan	nan
snan	-qnan	nan
-snan	+0	+1
-snan	-0	+1
-snan	inf	nan
-snan	-inf	nan
-snan	snan	nan
-snan	-snan	nan
-snan	qnan	nan
-snan	-qnan	nan
qnan	+0	+1
qnan	-0	+1
qnan	inf	nan
qnan	-inf	nan
qnan	snan	nan
qnan	-snan	nan
qnan	qnan	nan
qnan	-qnan	nan
-qnan	+0	+1
-qnan	-0	+1
-qnan	inf	nan
-qnan	-inf	nan
-qnan	snan	nan
-qnan	-snan	nan
-qnan	qnan	nan
-qnan	-qnan	nan

Dependencies

C: "km.h"

Examples

C interface:

    // typical usage
    double x1 = 0.0, x2 = -0.0, x3 = 1.5, x4 = -2.5;
    // special handling
    double a = INFINITY, b = -INFINITY, c = NAN;
    // print result
    printf("powr(0.0, -0.0) = %.15f\n", powr(x1, x2));
    printf("powr(-0.0, 0.0) = %.15f\n", powr(x2, x1));
    printf("powr(1.5, 1.5) = %.15f\n", powr(x3, x3));
    printf("powr(-2.5, 1.5) = %.15f\n", powr(x4, x3));
    printf("powr(INFINITY, 1.5) = %.15f\n", powr(a, x3));
    printf("powr(-INFINITY, 1.5) = %.15f\n", powr(b, x3));
    printf("powr(NAN, NAN) = %.15f\n", powr(c, c));
    return 0;

    /*
     * powr(0.0, -0.0) = 1.000000000000000
     * powr(-0.0, 0.0) = 1.000000000000000
     * powr(1.5, 1.5) = 1.837117307087384
     * powr(-2.5, 1.5) = nan
     * powr(INFINITY, 1.5) = inf
     * powr(-INFINITY, 1.5) = nan
     * powr(NAN, NAN) = nan
     */

Parent topic: Power and Root Functions