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ERF(P)POSIX Programmer's Manual ERF(P)NAMEerf, erff, erfl - error functionsSYNOPSIS#include <math.h> double erf(double x); float erff(float x); long double erfl(long double x);DESCRIPTIONThese 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 VALUEUpon 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.ERRORSThese 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.EXAMPLESNone.APPLICATION USAGEUnderflow 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.RATIONALENone.FUTURE DIRECTIONSNone.SEE ALSOerfc() , feclearexcept() , fetestexcept() , isnan() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Func- tions, <math.h>COPYRIGHTPortions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information TechnologyPortable 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 orig- inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .--IEEE/The Open Group 2003 ERF(P)

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