scalbn(), scalbnf()

Load the exponent of a radix-independent floating point number

Synopsis:

#include <math.h>

double scalbn ( double x,
                int n );

float scalbnf ( float x,
                int n );

Arguments:

x
The floating point number that you want to multiply by the exponent.
n
The exponent to apply to the radix of the machine's floating-point arithmetic.

Library:

libm

Use the -l m option to qcc to link against this library.

Description:

The scalbn() and scalbnf() functions compute x × r n , where r is the radix of the machine's floating point arithmetic.

Returns:

x × r n

When a correct value would cause an underflow, these functions return 0.0.

If an error occurs, these functions return 0, but this is also a valid mathematical result. If you want to check for errors, set errno to 0, call the function, and then check errno again. These functions don't change errno if no errors occurred.

Examples:

#include <stdio.h>
#include <errno.h>
#include <inttypes.h>
#include <math.h>
#include <fpstatus.h>

int main(int argc, char** argv) 
{
    double a, b, c, d;

    a = 10;
    b = 2;
    c = scalbn(a, b);
    d = sqrt(c/a);
    printf("Radix of machines fp arithmetic is %f \n", d);
    printf("So %f = %f * (%f ^ %f) \n", c, a, d, b);

    return(0);
}

produces the output:

Radix of machines fp arithmetic is 2.000000
So 40.000000 = 10.000000 * (2.000000 ^ 2.000000)

Classification:

ANSI, POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler No
Signal handler No
Thread Yes

Last modified: 2013-12-23

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