Computes ln(1+y) accurately.

    This function is supported on OpenVMS Integrity servers and
    Alpha only.

    Format

      #include  <math.h>

      double log1p  (double y);

      float log1pf  (float y);

      long double log1pl  (long double y);

1 - Argument

 y

    A real number greater than -1.

2 - Description

    The log1p functions compute ln(1+y) accurately, even for tiny y.

3 - Return Values

    x                  The natural logarithm of (1+y).
    -HUGE_VAL          y is less than -1 (errno is set to EDOM), or y
    NaN                y is NaN; errno is set to EDOM.