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log |
Portability: | ISO/ANSI C conforming, UNIX compatible |
SYNOPSIS | |
DESCRIPTION | |
RETURN VALUE | |
DIAGNOSTICS | |
EXAMPLE | |
RELATED FUNCTIONS | |
SEE ALSO |
SYNOPSIS |
#include <math.h> double log(double x);
DESCRIPTION |
log
computes the natural log of its argument
x
.
The
x
argument must be a positive double-precision,
floating-point number. The natural log is the inverse of the exponential
function.
RETURN VALUE |
log
returns the natural log of its argument
x
,
expressed as a double-precision, floating-point number.
DIAGNOSTICS |
The run-time library writes an error message
to the standard error file (
stderr
) if
x
is a negative number or 0. In this case, the
function returns
-HUGE_VAL
, the largest
negative floating-point number that can be represented.
If an error occurs in
log
, the
_matherr
routine is called.
You supply your own version of
_matherr
to suppress the diagnostic message or modify the value returned.
EXAMPLE |
This example computes the natural log
of 10, using
log
:
#include <math.h> #include <stdio.h> main() { double y, val; val = 10.0; y = log(val); printf("log(%f) = %f\n", val, y); }
RELATED FUNCTIONS |
SEE ALSO |
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