pow(), powf(), powl()

Raise a number to a given power


#include <math.h>

double pow( double x, 
            double y );

float powf( float x, 
            float y );

long double powl( long double x,
                  long double y );


The number you want to raise.
The power you want to raise the number to.



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


The pow(), powf(), and powl() functions compute x raised to the power of y.

To check for error situations, use feclearexcept() and fetestexcept(). For example:


The value of xy.

If x is: And y is: These functions return: Errors:
< 0.0, but finite Finite non-integer NaN FE_INVALID
0.0 < 0.0 Inf FE_DIVBYZERO
1.0 Any value, including NaN 1.0
Not 1.0 NaN NaN
Any value, including 0.0 and NaN ±0.0 1.0, but note that the correct mathematical result for 0.00.0 is undefined
NaN Nonzero NaN
±0.0 Any odd integer > 0.0 0.0, with the same sign as x
±0.0 Any even integer > 0.0 0.0
-1.0 ±Inf 1.0
|x| < 1.0 -Inf Inf
|x| > 1.0 -Inf 0.0
|x| < 1.0 Inf 0.0
|x| > 1.0 Inf Inf
-Inf An odd integer < 0.0 -0.0
-Inf A non-odd integer < 0.0 +0.0
-Inf An odd integer > 0.0 -Inf
-Inf A non-odd integer > 0.0 Inf
Inf < 0.0 0.0
Inf > 0.0 Inf
If the correct value would cause: These functions return: Errors:
Overflow Inf FE_OVERFLOW
Underflow and is representable The correct value, after rounding FE_UNDERFLOW

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.


#include <stdio.h>
#include <math.h>
#include <fenv.h>
#include <stdlib.h>

int main( void )
    int except_flags;


    printf( "%f\n", pow( 1.5, 2.5 ) );

    except_flags = fetestexcept(FE_ALL_EXCEPT);
    if(except_flags) {
        /* An error occurred; handle it appropriately. */

    return EXIT_SUCCESS;

produces the output:



ANSI, POSIX 1003.1

Cancellation point No
Interrupt handler No
Signal handler No
Thread Yes