scalbn

Compute the result of x * 2^y.

Interface Definition

C interface:

float scalbnf(float x, int y);

double scalbn(double x, int y);

long double scalbnl(long double x, int y);

Parameters

Parameter	Type	Description	Input/Output
x	For scalbnf, x is of single-precision floating-point type. For scalbn, x is of double-precision floating-point type. For scalbnl, x is of long double-precision floating-point type.	Floating-point value of the input data.	Input
y	For scalbnf, y is of integer type. For scalbn, y is of integer type. For scalbnl, y is of integer type.	Integer value of the input data	Input

Return Value

The result of x * 2^y is returned. If an overflow occurs, +∞ or -∞ is returned (the sign is the same as that of x).

Dependency

C: "km_l9.h"

Example

C interface:

    // typical usage
    double x1 = 0.0, x2 = -0.0, x3 = 2.0;
    long int y1 = 2, y2 = 3, y3 = 4, y4 = 5, y5 = 1100;
    // special handing
    double a = INFINITY, b = -INFINITY, c = NAN;
    printf("scalbn(0.0, 2) = %.15f\n", scalbn(x1, y1));
    printf("scalbn(-0.0, 3) = %.15f\n", scalbn(x2, y2));
    printf("scalbn(2.0, 4) = %.15f\n", scalbn(x3, y3));
    printf("scalbn(2.0, 5) = %.15f\n", scalbn(x3, y4));
    printf("scalbn(2.0, 1100) = %.15f\n", scalbn(x3, y5));
    printf("scalbn(INFINITY, 2) = %.15f\n", scalbn(a, y1));
    printf("scalbn(-INFINITY, 2) = %.15f\n", scalbn(b, y1));
    printf("scalbn(NAN, 2) = %.15f\n", scalbn(c, y1));
    /* 
     * scalbn(0.0, 2) = 0.000000000000000
     * scalbn(-0.0, 3) = -0.000000000000000
     * scalbn(2.0, 4) = 32.000000000000000
     * scalbn(2.0, 5) = 64.000000000000000
     * scalbn(2.0, 1100) = inf
     * scalbn(INFINITY, 2) = inf
     * scalbn(-INFINITY, 2) = -inf
     * scalbn(NAN, 2) = nan
     */

Parent topic: Exponential and Logarithmic Functions