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32.\" from: @(#)ieee.3 6.4 (Berkeley) 5/6/91
33.\" $Id: ieee_test.3,v 1.1 1994/03/11 17:19:01 jtc Exp $
34.\"
35.Dd March 10, 1994
36.Dt IEEE_TEST 3
37.Os
38.Sh NAME
39.Nm logb ,
40.Nm scalb ,
41.Nm significand
42.Nd IEEE test functions
43.Sh SYNOPSIS
44.Fd #include <math.h>
45.Ft double
46.Fn logb "double x"
47.Ft double
48.Fn scalb "double x" "double n"
49.Ft double
50.Fn significand "double x"
51.Sh DESCRIPTION
52These functions allow users to test conformance to
53.St -ieee754 .
54Their use is not otherwise recommended.
55.Pp
56.Fn logb x
57returns
58.Fa x Ns 's exponent
59.Fa n ,
60a signed integer converted to double\-precision floating\-point.
61.Fn logb \*(Pm\*(If
62= +\*(If;
63.Fn logb 0
64= -\*(If with a division by zero exception.
65.Pp
66.Fn scalbn x n
67returns
68.Fa x Ns \(**(2** Ns Fa n )
69computed by exponent manipulation.
70.Pp
71.Fn significand x
72returns
73.Fa sig ,
74where
75.Fa x
76:=
77.Fa sig No \(** 2** Ns Fa n
78with 1 \(<=
79.Fa sig
80< 2.
81.Fn significand x
82is not defined when
83.Fa x
84is 0, \*(Pm\*(If, or \*(Na.
85.Sh SEE ALSO
86.Xr ieee 3 ,
87.Xr math 3
88
89.Sh STANDARDS
90.St -ieee754