log1p(), log1pf()

Log(1+x)

Synopsis:

#include <math.h>

double log1p ( double x );

float log1pf ( float x );

Arguments:

x: The number that you want to add 1 to and compute the natural log of.

Library:

libm

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

Description:

The log1p() and log1pf() functions compute the value of log(1+x), where x > -1.0.

Returns:

If:	log1p() returns:
x = NAN	NAN
x < `-1.0`	-HUGE_VAL, or NAN (errno is set to EDOM).
x = `-1.0`	-HUGE_VAL (errno may be set to ERANGE).

If an error occurs, these functions return 0, but this is also a valid mathematical result. If you want to check for errors, set errno to 0, call the function, and then check errno again. These functions don't change errno if no errors occurred.

Classification:

ANSI, POSIX 1003.1

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

log1p, log1pf