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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" from: @(#)ieee.3 6.4 (Berkeley) 5/6/91 33.\" $FreeBSD$ 34.\" 35.Dd November 6, 2005 36.Dt ILOGB 3 37.Os 38.Sh NAME 39.Nm ilogb , 40.Nm ilogbf , 41.Nm ilogbl , 42.Nm logb , 43.Nm logbf 44.Nd extract exponent 45.Sh LIBRARY 46.Lb libm 47.Sh SYNOPSIS 48.In math.h 49.Ft int 50.Fn ilogb "double x" 51.Ft int 52.Fn ilogbf "float x" 53.Ft int 54.Fn ilogbl "long double x" 55.Ft double 56.Fn logb "double x" 57.Ft float 58.Fn logbf "float x" 59.Sh DESCRIPTION 60.Fn ilogb , 61.Fn ilogbf 62and 63.Fn ilogbl 64return 65.Fa x Ns 's exponent 66in integer format. 67.Fn ilogb \*(Pm\*(If 68returns 69.Dv INT_MAX , 70.Fn ilogb \*(Pm\*(Na 71returns 72.Dv FP_ILOGBNAN , 73and 74.Fn ilogb 0 75returns 76.Dv FP_ILOGB0 . 77.Pp 78.Fn logb x 79and 80.Fn logbf x 81return 82.Fa x Ns 's exponent 83in floating\-point format with the same precision as 84.Fa x . 85.Fn logb \*(Pm\*(If 86returns +\*(If, and 87.Fn logb 0 88returns -\*(If with a division by zero exception. 89.Sh SEE ALSO 90.Xr frexp 3 , 91.Xr ieee 3 , 92.Xr math 3 , 93.Xr scalbn 3 94.Sh STANDARDS 95The 96.Fn ilogb , 97.Fn ilogbf , 98.Fn ilogbl , 99.Fn logb 100and 101.Fn logbf 102routines conform to 103.St -isoC-99 . 104.Fn logb 105and 106.Fn logbf 107implement the logb function recommended by 108.St -ieee754 . 109.Sh HISTORY 110The 111.Fn logb 112function appeared in 113.Bx 4.3 . 114The 115.Fn ilogb 116function appeared in 117.Fx 1.1.5 . 118The 119.Fn ilogbf 120and 121.Fn logbf 122functions appeared in 123.Fx 2.0 . 124The 125.Fn ilogbl 126function appeared in 127.Fx 5.4 . 128