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# Technical Reference: Base Operating System and Extensions, Volume 1

## erfc, erfcf, or erfcl Subroutine

### Purpose

Computes the complementary error function.

### Syntax

#include <math.h>
float erfcf (x)
float x;
long double erfcl (x)
long double x;
double erfc (x)
double x;

### Description

The erfcf, erfcl, and erfc subroutines compute the complementary error function 1.0 - erf(x).

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

### Parameters

x |
Specifies the value to be computed. |

### Return Values

Upon successful completion, the erfcf, erfcl, and erfc subroutines return the value of
the complementary error function.

If the correct value would cause underflow and is not representable, a
range error may occur. Either 0.0 (if representable), or an implementation-defined
value is returned.

If x is NaN, a NaN is returned.

If x is ±0, +1 is returned.

If x is -Inf, +2 is returned.

If x is +Inf, +0 is returned.

If the correct value would cause underflow and is representable, a range
error may occur and the correct value is returned.

### Related Information

feclearexcept Subroutine, fetestexcept Subroutine, and class, _class, finite, isnan, or unordered Subroutines.

math.h in AIX 5L Version 5.2 Files Reference.

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