*Complementary error function*

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

`x`- The number for which you want to compute the complementary error function.

The erfc(), erfcf(), and erfcl()
functions calculate the
complementary error function of `x`
(i.e. the result of the error function,
erf(),
subtracted from `1.0`).
This is useful because the error function isn't very accurate
when `x` is large.

The erf() function computes:

This equality is true: erfc(-`x`) = 2 - erfc(`x`)

The value of the error function, or NAN
if `x` is NAN.
For a correct value that would cause an underflow, these functions return 0.0.

Note:
If an error occurs, these functions return 0, but this is also a valid
mathematical result.
If you want to check for errors, set
`errno`
to 0, call the function, and then check `errno` again.
These functions don't change `errno` if no errors occurred.

Safety: | |
---|---|

Cancellation point | No |

Interrupt handler | No |

Signal handler | No |

Thread | Yes |