posix man page for erfl

ERF(P)							     POSIX Programmer's Manual							    ERF(P)

NAME
       erf, erff, erfl - error functions

SYNOPSIS
       #include <math.h>

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

DESCRIPTION
       These functions shall compute the error function of their argument x, defined as:

       An  application	wishing  to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
       functions.  On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero,  an  error
       has occurred.

RETURN VALUE
       Upon successful completion, these functions shall return the value of the error function.

       If x is NaN, a NaN shall be returned.

       If x is +-0, +-0 shall be returned.

       If x is +-Inf, +-1 shall be returned.

       If x is subnormal, a range error may occur, and 2 * x/ sqrt(pi) should be returned.

ERRORS
       These functions may fail if:

       Range Error
	      The result underflows.

       If  the	integer  expression  (math_errhandling	&  MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression
       (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       Underflow occurs when |x| < DBL_MIN * ( sqrt(pi)/2).

       On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of  each  other,  but	at
       least one of them must be non-zero.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       erfc() , feclearexcept() , fetestexcept() , isnan() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
       Conditions for Mathematical Functions, <math.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
       and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								    ERF(P)