log, logl
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Header File
math.h
Category
Math Routines
Prototype
double log(double x);
long double logl(long double x);
Description
Calculates the natural logarithm of x.
log calculates the natural logarithm of x.
logl is the long double version; it takes a long double argument and returns a long double result.
Return Value
On success, log and logl return the value calculated, ln(x).
errno
EDOM |
Domain error |
If x is 0, the functions return the value negative HUGE_VAL (log) or negative _LHUGE_VAL (logl), and set errno to ERANGE. Error handling for these routines can be modified through the functions _matherr and _matherrl.
Example
#include <math.h> #include <stdio.h> int main(void) { double result; double x = 8.6872; result = log(x); printf("The natural log of %lf is %lf\n", x, result); return 0; }
Portability
POSIX | Win32 | ANSI C | ANSI C++ | |
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log |
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logl |
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