exp(), expf(), expl()

Compute the exponential function of a number

Synopsis:

#include <math.h>

double exp( double x );

float expf( float x );

long double expl( long double x );

Arguments:

x
The number for which you want to calculate the exponential.

Library:

libm

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

Description:

These functions compute the exponential function of x (i.e., ex).

A range error occurs if the magnitude of x is too large.

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

Returns:

The exponential value of x. For a correct value that would cause an underflow, these functions return 0.0 and a range error may occur.

If x is: These functions return:
NaN NaN
±0 1
-Inf +0
+Inf x

Errors:

FE_OVERFLOW
The result overflows.
FE_UNDERFLOW
The result underflows.

Examples:

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

int main( void )
{
    int except_flags;

    feclearexcept(FE_ALL_EXCEPT);

    printf( "%f\n", exp(.5) );

    except_flags = fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW);
    if(except_flags) {
        /* An error occurred; handle it appropriately. */
    }

    return EXIT_SUCCESS;
}

produces the output:

1.648721

Classification:

ANSI, POSIX 1003.1

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

Caveats:

The value of expm1(x) may be more accurate than exp(x) - 1.0 for small values of x.