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Synopsis:
    #include <math.h>
    double log( double x );

Description:
    The log function computes the natural logarithm (base e) of x.  A domain
    error occurs if the argument is negative.  A range error occurs if the
    argument is zero.

Returns:
    The log function returns the natural logarithm of the argument.  When
    the argument is outside the permissible range, the  matherr function is
    called.  Unless the default  matherr function is replaced, it will set
    the global variable  errno to  EDOM, and print a "DOMAIN error"
    diagnostic message using the  stderr stream.

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

    void main()
      {
        printf( "%f\n", log(.5) );
      }

    produces the following:

    -0.693147

Classification:
    ANSI

Systems:
    Math

See Also:
    exp, log10, log2, pow, matherr