November 2016
Beginner to intermediate
816 pages
19h 58m
Japanese
Content preview from Cクイックリファレンス 第2版
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28
2
章 型
2.3
浮動小数点型
Cは、任意の位置に小数点のある非整数を表す数値型も持つ。実数計算用の標準浮動小
数点型は次の通り。
float
単精度変数用
double
倍精度変数用
long double
拡張精度変数用
浮動小数点値は、表現に使われる2進書式と格納に使われるメモリ量で決まる限られた
精度しか格納できない。精度は有効桁数で表す。例えば、「6桁精度」「6有効数字」は、型
の2進表現が10進 6桁の実数を格納できる精度を持っていて、6桁の10進数に変換すれば、
元の6 桁の数値に戻ることを意味する。精度では、小数点の位置は関係ない。数値表現の
際に前後に補われる0は、有効数字の6 桁に数えない。数123,456,000と0.00123456はと
もに6 桁精度の型として格納できる。
Cでは、浮動小数点数の算術演算は通常
double
以上の精度で行う。実装内部の浮動小数
点精度はヘッダファイルfloat.hで定義されるマクロ
FLT_EVAL_METHOD
の値で示す。例えば、
マクロ
FLT_EVAL_METHOD
の値が1なら、次の積は
double
型で計算される。
float height = 1.2345, width = 2.3456; // Float
変数は単精度
double area = height * width; //
実際の計算は倍精度で行う
結果を
float
変数に代入すると値は丸められる。浮動小数点算術演算の詳細については
「16.3.11math.h」参照。
Cは浮動小数点型の記憶 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.