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.TH ILOGB 3M "Jul 12, 2006" "SunOS 5.11" "Mathematical Library Functions"
.SH NAME
ilogb, ilogbf, ilogbl \- return an unbiased exponent
.SH SYNOPSIS
.LP
.nf
c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
#include <math.h>

\fBint\fR \fBilogb\fR(\fBdouble\fR \fIx\fR);
.fi

.LP
.nf
\fBint\fR \fBilogbf\fR(\fBfloat\fR \fIx\fR);
.fi

.LP
.nf
\fBint\fR \fBilogbl\fR(\fBlong double\fR \fIx\fR);
.fi

.LP
.nf
cc [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
#include <math.h>

\fBint\fR \fBilogb\fR(\fBdouble\fR \fIx\fR);
.fi

.LP
.nf
\fBint\fR \fBilogbf\fR(\fBfloat\fR \fIx\fR);
.fi

.LP
.nf
\fBint\fR \fBilogbl\fR(\fBlong double\fR \fIx\fR);
.fi

.SH DESCRIPTION
.sp
.LP
These functions return the exponent part of their argument \fIx\fR.  Formally,
the return value is the integral part of  \fBlog\fR(r)| \fIx\fR | as a signed
integral value, for non-zero \fIx\fR, where \fIr\fR is the radix of the
machine's floating point arithmetic, which is the value of \fBFLT_RADIX\fR
defined in <\fBfloat.h\fR>.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, these functions return the exponent part of \fIx\fR
as a signed integer value. They are equivalent to calling the corresponding
\fBlogb\fR(3M) function and casting the returned value to type \fBint\fR.
.sp
.LP
If \fIx\fR is 0, the value \fBFP_ILOGB0\fR is returned. For SUSv3-conforming
applications compiled with the \fBc99\fR compiler driver (see
\fBstandards\fR(7)), a domain error occurs.
.sp
.LP
If \fIx\fR is \(+-Inf, the value \fBINT_MAX\fR is returned. For
SUSv3-conforming applications compiled with the \fBc99\fR compiler driver, a
domain error occurs.
.sp
.LP
If \fIx\fR is NaN, the value \fBFP_ILOGBNAN\fR is returned. For
SUSv3-conforming applications compiled with the \fBc99\fR compiler driver, a
domain error occurs.
.SH ERRORS
.sp
.LP
These functions will fail if:
.sp
.ne 2
.mk
.na
\fBDomain Error\fR
.ad
.RS 16n
.rt
The \fIx\fR argument is zero, NaN, or \(+-Inf.
.sp
If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
non-zero, then the invalid floating-point exception is raised.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
tab(	) box;
cw(2.75i) |cw(2.75i)
lw(2.75i) |lw(2.75i)
.
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR limits.h (3HEAD),
.BR math.h (3HEAD),
.BR feclearexcept (3M),
.BR fetestexcept (3M),
.BR logb (3M),
.BR scalb (3M),
.BR attributes (7),
.BR standards (7)