ERF(3M)                                                                ERF(3M)



NAME
     erf, erfc, erfl, erfcl - error function and complementary error function

SYNOPSIS
     #include <math.h>

     double erf (double x);

     double erfc (double x);

     long double erfl (long double x);

     long double erfcl (long double x);

DESCRIPTION
     erf returns the error function of x, defined as

             (2 / sqrt(pi)) integral{0 to x} 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 (e.g., for x = 10, 12 places are lost).

     The standard math library libm.a, libmx.a, and libm43.a each contain
     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.

DIAGNOSTICS
     In the diagnostics below, functions in the standard math library libm.a,
     are referred to as -lm versions, those in math library libmx.a are
     referred to as -lmx versions, and those in the the BSD math library
     libm43.a are referred to as -lm43 versions.  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 -lm43 versions to
     return the same argument.  The -lm43 versions never set errno.

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

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












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