log, logf, logl
From cppreference.com
| Defined in header <math.h>
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| float logf( float arg ); |
(1) | (since C99) |
| double log( double arg ); |
(2) | |
| long double logl( long double arg ); |
(3) | (since C99) |
| Defined in header <tgmath.h>
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| #define log( arg ) |
(4) | (since C99) |
1-3) Computes the natural (base e) logarithm of
arg.4) Type-generic macro: If
arg has type long double, logl is called. Otherwise, if arg has integer type or the type double, log is called. Otherwise, logf is called. If arg is complex or imaginary, then the macro invokes the corresponding complex function (clogf, clog, clogl).Parameters
| arg | - | floating point value |
Return value
If no errors occur, the natural (base-e) logarithm of arg (ln(arg) or log
e(arg)) is returned.
If a domain error occurs, an implementation-defined value is returned (NaN where supported).
If a pole error occurs, -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL is returned.
Error handling
Errors are reported as specified in math_errhandling.
Domain error occurs if arg is less than zero.
Pole error may occur if arg is zero.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- If the argument is ±0, -∞ is returned and FE_DIVBYZERO is raised.
- If the argument is 1, +0 is returned
- If the argument is negative, NaN is returned and FE_INVALID is raised.
- If the argument is +∞, +∞ is returned
- If the argument is NaN, NaN is returned