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.\"     from: @(#)ieee.3	6.4 (Berkeley) 5/6/91
.\" %FreeBSD: src/lib/msun/man/ieee.3,v 1.5.2.2 2001/03/06 16:46:24 ru Exp %
.\"
.\" $FreeBSD$
.Dd February 25, 1994
.Dt IEEE 3
.Os
.Sh 名称
.Nm copysign ,
.Nm copysignf ,
.Nm finite ,
.Nm finitef ,
.Nm ilogb ,
.Nm ilogbf ,
.Nm nextafter ,
.Nm nextafterf ,
.Nm remainder ,
.Nm remainderf ,
.Nm scalbn ,
.Nm scalbnf
.Nd IEEE 演算関数
.Sh 書式
.Fd #include <math.h>
.Ft double 
.Fn copysign "double x" "double y"
.Ft float 
.Fn copysignf "float x" "float y"
.Ft int 
.Fn finite "double x"
.Ft int 
.Fn finitef "float x"
.Ft int
.Fn ilogb "double x"
.Ft int
.Fn ilogbf "float x"
.Ft double 
.Fn nextafter "double x" "double y"
.Ft float
.Fn nextafterf "float x" "float y"
.Ft double
.Fn remainder "double x" "double y"
.Ft float
.Fn remainderf "float x" "float y"
.Ft double 
.Fn scalbn "double x" "int n"
.Ft float 
.Fn scalbnf "float x" "int n"
.Sh 解説
これらの関数は、
.St -ieee754
によって要求または推奨されています。
.Pp
.Fn copysign
および
.Fn copysignf
は、
.Fa x
の符号を
.Fa y
の符号に置き換えて
.Fa x
を返します。
.Pp
\-\*(If \*(Lt
.Fa x
\*(Lt +\*(If
の時には、
.Fn finite
および
.Fn finitef
は、値 1 を返します。そうでない時 (
.Pf \\*(Ba Ns Fa x Ns \\*(Ba
= \*(If または
.Fa x
が \*(Na の時) には、0 が返されます。
.Pp
.Fn ilogb
および
.Fn ilogbf
は、
.Fa x
の
.Fa n
乗を整数型で返します。
.Fn ilogb \*(Pm\*(If 
は
.Dv INT_MAX
を返し、
.Fn ilogb 0
は
.Dv INT_MIN
を返します。
.Pp
.Fn nextafter 
および
.Fn nextafterf
は、次のマシン表示可能な数を
.Fa x
から
.Fa y
方向に返します。
.Pp
.Fn remainder
および
.Fn remainderf
は、剰余
.Fa r
:=
.Fa x
\-
.Fa n\(**y
を返します。このとき
.Fa n
は
.Bk -words
.Fa x Ns / Ns Fa y
.Ek
の正確な値に最も近い整数です。更に、
.Pf \\*(Ba Fa n
\-
.Sm off
.Fa x No / Fa y No \\*(Ba
.Sm on
=
1/2
ならば、
.Fa n
は偶数です。その結果、剰余は正確に計算され、
.Sm off
.Pf \\*(Ba Fa r No \\*(Ba
.Sm on
\*(Le
.Sm off
.Pf \\*(Ba Fa y No \\*(Ba/2
.Sm on
となります。しかし、
.Fn remainder x 0
および
.Fn remainder \*(If 0
は、\*(Na を生成する無効な演算です。
.Pp
.Fn scalbn
および
.Fn scalbnf
は、指数操作によって計算された
.Fa x Ns \(**(2** Ns Fa n )
を返します。
.Sh 関連項目
.Xr math 3
.Sh 歴史
.Nm ieee
関数は、
.Bx 4.3
で登場しました。
.Sh 規格
.St -ieee754