| .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de) |
| .\" Distributed under GPL |
| .\" Based on glibc infopages |
| .TH SIGNBIT 3 2002-08-10 "GNU" "libc math functions" |
| .SH NAME |
| signbit \- test sign of a real floating point number |
| .SH SYNOPSIS |
| .B "#include <math.h>" |
| .sp |
| .BI "int signbit (" X ");" |
| .sp |
| Compile with \-std=c99; link with \-lm. |
| .SH DESCRIPTION |
| `signbit' is a generic macro which can work on all real floating-point |
| types. It returns a non-zero value if the value of X has its sign |
| bit set. |
| .PP |
| This is not the same as `x < 0.0', because IEEE 754 floating point |
| allows zero to be signed. The comparison `\-0.0 < 0.0' is false, |
| but `signbit (\-0.0)' will return a non-zero value. |
| .SH "CONFORMING TO" |
| This function is defined in IEC 559 (and the appendix with |
| recommended functions in IEEE 754/IEEE 854). |
| .SH "SEE ALSO" |
| .BR copysign (3) |