.\" Copyright (c) 1985, 1991 The Regents of the University of California. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" from: @(#)floor.3 6.5 (Berkeley) 4/19/91 .\" $Id: ilogb.3,v 1.7 2006/06/16 18:49:26 scanon Exp $ .\" .Dd December 11, 2006 .Dt ILOGB 3 .Os .Sh NAME .Nm ilogb .Nd return exponent as an integer value .Sh SYNOPSIS .Fd #include <math.h> .Ft int .Fn ilogb "double x" .Ft int .Fn ilogbl "long double x" .Ft int .Fn ilogbf "float x" .Sh DESCRIPTION The .Fn ilogb functions return the exponent of x as a signed integer value. .Sh SPECIAL VALUES .Fn ilogb "±0" returns FP_ILOGB0. .Pp .Fn ilogb "±infinity" returns INT_MAX. .Pp .Fn ilogb "x" returns FP_ILOGBNAN if x is a NaN. .Pp A range error may occur if x is 0, ±infinity, or a nan. .Pp The special return values FP_ILOGB0 and FP_ILOGBNAN are defined in math.h, and may differ between platforms. INT_MAX is defined in limits.h. .Sh SEE ALSO .Xr math 3 .Sh STANDARDS The .Fn ilogb functions conform to ISO/IEC 9899:1999(E).