就是log
MSDN解释如下....
log, log10
Calculates logarithms.
double log( double x );
double log10( double x );
Routine Required Header Compatibility
log <math.h> ANSI, Win 95, Win NT
log10 <math.h> ANSI, Win 95, Win NT
For additional compatibility information, see Compatibility in the Introduction.
Libraries
LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version
Return Value
The log functions return the logarithm of x if successful. If x is
negative, these functions return an indefinite (same as a quiet NaN).
If x is 0, they return INF (infinite). You can modify error handling by
using the _matherr routine.
Parameter
x
Value whose logarithm is to be found
Example
/* LOG.C: This program uses log and log10
* to calculate the natural logarithm and
* the base-10 logarithm of 9,000.
*/
#include <math.h>
#include <stdio.h>
void main( void )
{
double x = 9000.0;
double y;
y = log( x );
printf( "log( %.2f ) = %f\n", x, y );
y = log10( x );
printf( "log10( %.2f ) = %f\n", x, y );
}
Output
log( 9000.00 ) = 9.104980
log10( 9000.00 ) = 3.954243
Floating-Point Support Routines
See Also exp, _matherr, pow
[此贴子已经被作者于2005-12-6 23:19:13编辑过]
2005-12-05 18:07
