erfc, erfcf, erfcl - complementary error function
#include <math.h> double erfc(double x); float erfcf(float x); long double erfcl(long double x); Link with -lm. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): erfc(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE erfcf(), erfcl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
These functions return the complementary error function of x, that is, 1.0 - erf(x).
On success, these functions return the complementary error function of x, a value in the range [0,2]. If x is a NaN, a NaN is returned. If x is +0 or -0, 1 is returned. If x is positive infinity, +0 is returned. If x is negative infinity, +2 is returned. If the function result underflows and produces an unrepresentable value, the return value is 0.0. If the function result underflows but produces a representable (i.e., subnormal) value, that value is returned, and a range error occurs.
See math_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur: Range error: result underflow (result is subnormal) An underflow floating-point exception (FE_UNDERFLOW) is raised. These functions do not set errno.
For an explanation of the terms used in this section, see attributes(7). Interface Attribute Value erfc(), erfcf(), erfcl() Thread safety MT-Safe
C99, POSIX.1-2001, POSIX.1-2008. The variant returning double also conforms to SVr4, 4.3BSD.
The erfc(), erfcf(), and erfcl() functions are provided to avoid the loss accuracy that would occur for the calculation 1-erf(x) for large values of x (for which the value of erf(x) approaches 1).
cerf(3), erf(3), exp(3)
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