Implementation status: to be implemented

Synopsis

#include <math.h>

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

Description

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

${2 over sqrt pi} int from 0 to x e"^" " "{- t"^" 2" "} dt$

Arguments:

x - the argument for which the error function is calculated,

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

On success the functions return the value of the error function.

If x is NaN, a NaN is returned.

If x is ±0, ±0 is returned.

If x is ±Inf, ±1 is returned.

If the correct value would cause underflow, a range error occurs, and erf(), erff(), and erfl() return DBL_MIN-1, FLT_MIN-1, and LDBL_MIN-1, respectively.

Errors

[ERANGE] The result underflows.

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

Implementation tasks

  • Implement the erf() function.
  • Implement the erff() function.
  • Implement the erfl() function.