log10

Common logarithm.

SYNOPSIS:

double x, y, log10();
y = log10(x);

DESCRIPTION:

Returns logarithm to the base 10 of x.

The argument is separated into its exponent and fractional parts. The logarithm of the fraction is approximated by:

     log(1+x) = x - 0.5 x**2 + x**3 P(x)/Q(x).

ACCURACY:
                      Relative error:
arithmetic   domain     # trials      peak         rms
    IEEE      0.5, 2.0     30000      1.5e-16     5.0e-17
    IEEE      0, MAXNUM    30000      1.4e-16     4.8e-17
    DEC       1, MAXNUM    50000      2.5e-17     6.0e-18

In the tests over the interval [1, MAXNUM], the logarithms of the random arguments were uniformly distributed over [0, MAXLOG].

ERROR MESSAGES:

singularity: x = 0; returns -INFINITY
domain:       x < 0; returns NAN