Conference rusure::math

1728.0. "erf, anyone?" by CSC32::J_HENSON (Faster than a speeding ticket) Thu Mar 11 1993 21:22

In the Unix/Ultrix world, there is a mathematics library, libm.  That's
pretty much all that I now about it.

Two of the routines are ERF and ERFC.  I am including the definitions
of the functions below.  What I need to know, though, is there a VMS
equivalent (RTL or otherwise), and if there is, what is it.

Thanks,

Jerry Henson
U.S. CSC

P.S.  Posted in the following conferences:  Math, VaxC, POSIX, RTL

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 erf,erfc - error function

SYNTAX

 #include <math.h>

 double erf(x)
 double x;

 double erfc(x)
 double x;

DESCRIPTION

 The erf function returns the error function of x defined as follows.

erf(x) = 2/sqrt(pi)*integral from 0 to x of exp(-t*t) dt.

 The erfc function returns 1.0-erf(x).

 The entry for the erfc function is provided because of the extreme loss
 of relative accuracy if erf(x) is called for large x and the result
 subtracted from 1.  For example if x=10, 12 places are lost.

RETURN VALUE

 The erf and erfc functions return NaN when x is NaN.