Log(1+x)
#include <math.h> double log1p ( double x ); float log1pf ( float x ); long double log1pl( long double x );
The log1p(), log1pf(), and log1pl() functions compute the value of log(1+x), where x > -1.0.
To check for error situations, use feclearexcept() and fetestexcept(). For example:
log(1+x)
| If x is: | These functions return: | Errors: |
|---|---|---|
| x is -1.0 | -Inf | FE_DIVBYZERO |
| Less than -1.0 and finite, or -Inf | NaN | FE_INVALID |
| ±0.0 | x | — |
| Inf | Inf | — |
| NaN | NaN | — |
| Subnormal | x | — |
These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.
| Safety: | |
|---|---|
| Cancellation point | No |
| Interrupt handler | No |
| Signal handler | No |
| Thread | Yes |