log10

log10

Compute the Common Logarithm

Portability: ISO/ANSI C conforming, UNIX compatible

SYNOPSIS
DESCRIPTION
RETURN VALUE
DIAGNOSTICS
EXAMPLE
RELATED FUNCTIONS
SEE ALSO

SYNOPSIS

#include <math.h>

double log10(double x);

DESCRIPTION

log10 computes the common (base 10) log of its argument x . The x argument must be a positive double-precision, floating-point number.

RETURN VALUE

log10 returns the common log of its argument, expressed as a double-precision, floating-point number.

DIAGNOSTICS

If x is negative or 0, log10 returns -HUGE_VAL . In this case, the run-time library also writes an error message to the standard error file ( stderr ).

If an error occurs in log10 , 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 calculates the common log of RATE, and rounds up using log10 :

#include <math.h>
#include <stdio.h>

#define RATE .017

main()
{
   double y;
   y = ceil(log10(RATE));

      /* Print the "order of magnitude" of RATE. */
   printf("ceil(log10(%f)) = %f\n", RATE, y);
}

RELATED FUNCTIONS

log , _matherr

SEE ALSO

Mathematical Functions

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