expm1

Exponential functions

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Contents

Interface
Description
Special Values
See Also
Standards
Page Comments

Interface

#include <math.h>
double  exp (double x)
long  expl (long double x)
float  expf (float x)
double  exp2 (double x)
long  exp2l (long double x)
float  exp2f (float x)
double  expm1 (double x)
long  expm1l (long double x)
float  expm1f (float x)

Description

The exp function computes $\inline e^x$ , the base-e exponential of x.

The exp2 function computes $\inline 2^x$ , the base-2 exponential of x.

The expm1 function computes the base-e exponential of x, minus 1, accurately even for very small values of x.

Example:

Example - Exponential functions

Workings

#include <stdio.h>
#include <math.h>
int main(void)
{
  double result, x = 4.34;
  result = exp(x);
  printf("'e' raised to the power of %.2lf (e^%.2lf) = %.2lf\n", x, x, result);
  return 0;
}

Solution

Output:

'e' raised to the power of 4.34 (e^4.34) = 76.71

Special Values

exp ( ±0 ) and exp2 ( ±0 ) return 1.

exp ( -∞ ) and exp2 ( -∞ ) return +0.

exp ( +∞ ) and exp2 ( +∞ ) return +∞.

expm1 ( ±0 ) returns ±0.

expm1 ( -∞ ) returns -1.

expm1 ( +∞ ) returns +∞.

For all these functions, a range error occurs if the magnitude of x is too large.

Standards

The exp, exp2 and expm1 functions conform to ISO/IEC 9899:1999(E).

double	`exp` (double x)
long	`expl` (long double x)
float	`expf` (float x)
double	`exp2` (double x)
long	`exp2l` (long double x)
float	`exp2f` (float x)
double	`expm1` (double x)
long	`expm1l` (long double x)
float	`expm1f` (float x)