1.\" Copyright (c) 1985, 1991 Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" from: @(#)ieee.3 6.4 (Berkeley) 5/6/91 29.\" $FreeBSD$ 30.\" 31.Dd November 6, 2005 32.Dt ILOGB 3 33.Os 34.Sh NAME 35.Nm ilogb , 36.Nm ilogbf , 37.Nm ilogbl , 38.Nm logb , 39.Nm logbf 40.Nd extract exponent 41.Sh LIBRARY 42.Lb libm 43.Sh SYNOPSIS 44.In math.h 45.Ft int 46.Fn ilogb "double x" 47.Ft int 48.Fn ilogbf "float x" 49.Ft int 50.Fn ilogbl "long double x" 51.Ft double 52.Fn logb "double x" 53.Ft float 54.Fn logbf "float x" 55.Sh DESCRIPTION 56.Fn ilogb , 57.Fn ilogbf 58and 59.Fn ilogbl 60return 61.Fa x Ns 's exponent 62in integer format. 63.Fn ilogb \*(Pm\*(If 64returns 65.Dv INT_MAX , 66.Fn ilogb \*(Pm\*(Na 67returns 68.Dv FP_ILOGBNAN , 69and 70.Fn ilogb 0 71returns 72.Dv FP_ILOGB0 . 73.Pp 74.Fn logb x 75and 76.Fn logbf x 77return 78.Fa x Ns 's exponent 79in floating\-point format with the same precision as 80.Fa x . 81.Fn logb \*(Pm\*(If 82returns +\*(If, and 83.Fn logb 0 84returns -\*(If with a division by zero exception. 85.Sh SEE ALSO 86.Xr frexp 3 , 87.Xr ieee 3 , 88.Xr math 3 , 89.Xr scalbn 3 90.Sh STANDARDS 91The 92.Fn ilogb , 93.Fn ilogbf , 94.Fn ilogbl , 95.Fn logb 96and 97.Fn logbf 98routines conform to 99.St -isoC-99 . 100.Fn logb 101and 102.Fn logbf 103implement the logb function recommended by 104.St -ieee754 . 105.Sh HISTORY 106The 107.Fn logb 108function appeared in 109.Bx 4.3 . 110The 111.Fn ilogb 112function appeared in 113.Fx 1.1.5 . 114The 115.Fn ilogbf 116and 117.Fn logbf 118functions appeared in 119.Fx 2.0 . 120The 121.Fn ilogbl 122function appeared in 123.Fx 5.4 . 124