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.\" 3. 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.Dd December 16, 2007 29.Dt ILOGB 3 30.Os 31.Sh NAME 32.Nm ilogb , 33.Nm ilogbf , 34.Nm ilogbl , 35.Nm logb , 36.Nm logbf , 37.Nm logbl 38.Nd extract exponent 39.Sh LIBRARY 40.Lb libm 41.Sh SYNOPSIS 42.In math.h 43.Ft int 44.Fn ilogb "double x" 45.Ft int 46.Fn ilogbf "float x" 47.Ft int 48.Fn ilogbl "long double x" 49.Ft double 50.Fn logb "double x" 51.Ft float 52.Fn logbf "float x" 53.Ft long double 54.Fn logbl "long double 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 , 75.Fn logbf x , 76and 77.Fn logbl x 78return 79.Fa x Ns 's exponent 80in floating\-point format with the same precision as 81.Fa x . 82.Fn logb \*(Pm\*(If 83returns +\*(If, and 84.Fn logb 0 85returns -\*(If with a division by zero exception. 86.Sh SEE ALSO 87.Xr frexp 3 , 88.Xr ieee 3 , 89.Xr math 3 , 90.Xr scalbn 3 91.Sh STANDARDS 92The 93.Fn ilogb , 94.Fn ilogbf , 95.Fn ilogbl , 96.Fn logb , 97.Fn logbf , 98and 99.Fn logbl 100routines conform to 101.St -isoC-99 . 102The latter three 103implement the logb function recommended by 104.St -ieee754 . 105.Sh HISTORY 106.Bl -tag -width "Function " -compact 107.It Em Function 108.Em "First Appeared In" 109.It Fn logb 110.Bx 4.3 111.It Fn ilogb 112.Fx 1.1.5 113.It Fn ilogbf 114.Fx 2.0 115.It Fn logbf 116.Fx 2.0 117.It Fn ilogbl 118.Fx 5.4 119.It Fn logbl 120.Fx 8.0 121.El 122