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Log(1+x)
#include <math.h>
double log1p ( double x );
float log1pf ( float x );
- x
- The number that you want to add 1 to and compute the natural log of.
libm
Use the -l m option to
qcc
to link against this library.
The log1p() and log1pf() functions compute the value of
log(1+x),
where x > -1.0.
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. |
ANSI,
POSIX 1003.1
Safety: | |
Cancellation point |
No |
Interrupt handler |
No |
Signal handler |
No |
Thread |
Yes |
ilogb(),
log(),
logb(),
log10()
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