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.\"     from: @(#)ieee.3	6.4 (Berkeley) 5/6/91
.\"	%Id: ieee.3,v 1.4 1997/02/22 15:09:35 peter Exp %
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.\" $FreeBSD$
.Dd Feb 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論理演算
.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
により要求または推奨されています。
.Pp
.Fn copysign
と
.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
のとき、
.Fn finite
と
.Fn finitef
は値 1 を返します。
その他
( 
.Pf \\*(Ba Ns Fa x Ns \\*(Ba
= \*(If
または
.Fa x
が \*(Na の時 )
はゼロを返します。
.Pp
.Fn ilogb
と
.Fn ilogbf
は
.Fa x
の
.Fa n
乗を整数値で返します。
.Fn ilogb \*(Pm\*(If
は
.Dv INT_MAX
を戻し、
.Fn ilogb 0
は
.Dv INT_MIN
を返します。
.Pp
.Fn nextafter
と
.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
と
.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
の完全な値に最も近似の整数です。さらに、
.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。
この結果、剰余は完全に計算されて、
.Sm off
.Pf \\*(Ba Fa r No \\*(Ba
.Sm on
\*(Le
.Sm off
.Pf \\*(Ba Fa y No \\*(Ba/2
.Sm on
になります。しかし、
.Fn remainder x 0
と
.Fn remainder \*(If 0
は \*(Na を作る無効の演算です。
.Pp
.Fn scalbn
と
.Fn scalbnf
は指数操作で計算される
.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
から登場しました。
.Sh 規格
.St -ieee754