ERF(3M)ERF(3M)


NAME
     erf, erff, erfcf, erfcl, erfc, derf, derfc, erfl, erfcl, qerf, qerfc -
     Error function and complementary error function

SYNOPSIS
     Fortran synopsis:
          real*4 r1, r2, erf
          real*8 dp1, dp2, derf
          real*16 cd1, cd2, qerf

          r2 = erf(r1)
          dp2 = derf(dp1)
          cd2 = qerf(cd1)

          real*4 r1, r2, erfc
          real*8 dp1, dp2, derfc
          real*16 cd1, cd2, qerfc

          r2 = erfc(r1)
          dp2 = derfc(dp1)
          cd2 = qerfc(cd1)

     C synopsis:
          #include <math.h>

          double erf (double x);
          float erff(float x);
          long double erfl (long double x);

          double erfc (double x);
          float erfcf(float x);
          long double erfcl (long double x);

DESCRIPTION
     Alternate entries exist for several routines.  The following lists
     these routines and the ANSI standard name and the alternate entry
     name:

     ANSI standard name       Alternate name

     erfcl                    qerf

     erfcl                    qerfc

     The erfcf functions and the erff functions are not available for
     programs compiled with the O32 ABI.

     The erf intrinsic functions return the error function of x, defined in
     the following:


(2/sqrt(pi))integral{0tox}of(e
-t
2

                                                ) 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. For example, if x = 10, 12 places are
     lost.

     The libraries libm.a, libmx.a, and libm43.a each contain versions of
     these functions.

     C/C++: each library contains versions of erf and erfc; however the
     long double-precision routines erfl and erfcl are only available in
     the standard math library, -lm and in -lmx.

NOTES
     Long double operations on this system are only supported in round to
     nearest rounding mode (the default).  The system must be in round to
     nearest rounding mode when calling any of the long double functions,
     or incorrect answers will result.

RETURN VALUES
     Functions in the standard math library (libm.a) are referred to as
     -lm; versions in the mathx library (libmx.a) are referred to as -lmx,
     and those in the the BSD math library (libm43.a) are referred to as
     -ilm43.

     The -lm and -lmx versions always return the default Quiet NaN and set
     errno to EDOM when a NaN is used as an argument.  A NaN argument
     usually causes the -ilm43 versions to return the same argument.  The
     -ilm43 versions never set errno.

     See matherr(3M) for a description of error handling for -lmx
     functions.

SEE ALSO
     exp(3M), matherr(3M)