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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46
4
章 型変換
ログラマにプログラムの型変換が意図的なものであることを示す。例えば、関数の戻り値
の破棄に明示的
void
型変換を使えば、関数が返すエラーを無視していることに注意を向け
させることができる。
しかし、コンパイラの暗黙的型変換を説明する本章の例では、本当に必要でない限りキャ
スト演算子を使わない。
4.1
算術型の変換
算術型の間では型変換が常に可能であり、コンパイラは必要なら暗黙に型変換を行う。
変換は、新しい型で式の値が表現可能なら、値を保存する。これは常に可能なわけではな
い。例えば、負値を符号なし型に、あるいは、型
double
で小数部分がある浮動小数点数を
型
int
に変換する場合、新しい型は元の値を表現できない。その場合、コンパイラは警告を
発する。
4.1.1
型階層
算術オペランドが異なる型に使われたとき、型の変換ランクに従って暗黙的型変換が実
行される。型は次の規則でランク付けられる。
●
2つの符号なし整数型は変換ランクが異なり得る。幅の広いほうがランクが高い。
●
符号付き整数型は対応する符号なし整数型と同じランクを持つ。型
char
は
signed
char
および
unsigned char
と同じランクを持つ。
●
標準整数型のランクは次の順序となる。
_Bool < char < short < int < long < long long
●
標準整数型は同じ幅の拡張整数型（拡張整数型は「2.2.1.1正確なビット幅の整数型
（C99）」参照）よりランクが高い。
●
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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.