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Michael Kerrisk 2007-12-17 17:04:19 +00:00
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21
man3/signbit.3
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@ -7,18 +7,25 @@ signbit \- test sign of a real floating point number
.SH SYNOPSIS
.B "#include <math.h>"
.sp
.BI "int signbit(" X ");"
.BI "int signbit(" x ");"
.sp
Compile with \fI\-std=c99\fP; link with \fI\-lm\fP.
.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.
.BR signbit ()
is a generic macro which can work on all real floating-point types.
It returns a non-zero value if the value of
.I x
has its sign bit set.
.PP
This is not the same as `x < 0.0', because IEEE 754 floating point
This is not the same as
.IR "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.
The comparison
.IR "-0.0 < 0.0"
is false, but
.IR "signbit(\-0.0)"
will return a non-zero value.
.SH "CONFORMING TO"
C99.
This function is defined in IEC 559 (and the appendix with