function
<cmath> <ctgmath>
log1p
double log1p (double x); float log1pf (float x);long double log1pl (long double x);
double log1p (double x); float log1p (float x);long double log1p (long double x); double log1p (T x); // additional overloads for integral types
Compute logarithm plus one
Returns the natural logarithm of one plus x.
For small magnitude values of x, logp1 may be more accurate than log(1+x).
Header
<tgmath.h> provides a type-generic macro version of this function.
Additional overloads are provided in this header (
<cmath>) for the
integral types: These overloads effectively cast
x to a
double before calculations (defined for
T being any
integral type).
Parameters
- x
- Value whose logarithm is calculated.
If the argument is less than -1, a domain error occurs.
Example
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/* log1p example */
#include <stdio.h> /* printf */
#include <math.h> /* log1p */
int main ()
{
double param, result;
param = 1.0;
result = log1p (param);
printf ("log1p (%f) = %f.\n", param, result );
return 0;
}
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Output:
log1p (1.000000) = 0.693147
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See also
- exp
- Compute exponential function (function)
- log
- Compute natural logarithm (function)
- pow
- Raise to power (function)