erf(3M)                        DG/UX R4.11MU05                       erf(3M)


NAME
       erf, erfc - error function and complementary error function

SYNOPSIS
       cc [flag ...] file ...  -lm [library ...]

       #include <math.h>

       double erf (double x);

       double erfc (double x);

DESCRIPTION
       erf returns the error function of x, defined as

              2/sqrt(pi)*integral from 0 to x of e^(-t²)dt

       erfc, which returns 1.0 - erf(x), is provided because of the extreme
       loss of relative accuracy if erf(x) is called for large x and the
       result subtracted from 1.0 (e.g., for x = 5, 12 places are lost).

   Considerations for Threads Programming
                     +---------+-----------------------------+
                     |         |                      async- |
                     |function | reentrant   cancel   cancel |
                     |         |             point     safe  |
                     +---------+-----------------------------+
                     |erf      |     Y         N        N    |
                     |erfc     |     Y         N        N    |
                     +---------+-----------------------------+
DIAGNOSTICS
       For each of these functions, if x is a quiet NaN, that value is
       returned.  If x is a signaling NaN, a quiet NaN is returned and an
       invalid operation exception is raised.  In either case, errno is set
       to EDOM, and a message indicating DOMAIN error is printed on the
       standard error output.

       When the -Xt compilation option is used, these error handling
       procedures may be changed with the function matherr.  When the -Xa or
       -Xc compilation options are used, no error messages are printed.

SEE ALSO
       cc(1), reentrant(3), exp(3M), fpsetmask(3C).


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