blog/content/post/2008/03/23/2008-03-23-00000857.md

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---
title: '『[新版C言語プログラミングレッスン 入門編』 第四章 if'
author: kazu634
date: 2008-03-23
wordtwit_post_info:
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categories:
- C
- Programming
---
<div class="section">
<p>
 つづきだよー
</p>
<p>
<a name="seemore"></a>
</p>
<h4>
論理和「||」
</h4>
<pre class="syntax-highlight">
<span class="synPreProc">#include </span><span class="synConstant">&#60;stdio.h&#62;</span>
<span class="synPreProc">#include </span><span class="synConstant">&#60;stdlib.h&#62;</span>
<span class="synPreProc">#define MAX_LINE </span><span class="synConstant">128</span><span class="synPreProc"> </span><span class="synComment">/* 入力行の最大長 */</span>
<span class="synType">int</span> main(<span class="synType">void</span>);
<span class="synType">int</span> main(<span class="synType">void</span>)
{
<span class="synType">char</span> buf[MAX_LINE];
<span class="synType">int</span> n;
printf (<span class="synConstant">&#34;降水確率を入力してください。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
gets(buf);
n = atoi(buf);
printf (<span class="synConstant">&#34;降水確率は </span><span class="synSpecial">%d</span><span class="synConstant"> </span><span class="synSpecial">%%</span><span class="synConstant">です。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>, n);
<span class="synStatement">if</span> (n &#60; <span class="synConstant"></span> || <span class="synConstant">100</span> &#60; n) {
printf (<span class="synConstant">&#34;降水確率は0 - 100の間ですよ。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synStatement">else</span> <span class="synStatement">if</span> (n &#62;= <span class="synConstant">50</span>) {
printf (<span class="synConstant">&#34;傘を忘れずにね。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synStatement">else</span> {
printf (<span class="synConstant">&#34;傘はいりません。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
printf (<span class="synConstant">&#34;いってらっしゃい</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
<span class="synStatement">return</span>(<span class="synConstant"></span>);
}
</pre>
<p>
or は「||」で表現する。
</p>
<h4>
現在の時間を入力してもらって、それに応じたメッセージを表示させる
</h4>
<pre class="syntax-highlight">
<span class="synPreProc">#include </span><span class="synConstant">&#60;stdio.h&#62;</span>
<span class="synPreProc">#include </span><span class="synConstant">&#60;stdlib.h&#62;</span>
<span class="synPreProc">#define MAX_LINE </span><span class="synConstant">128</span><span class="synPreProc"> </span><span class="synComment">/* 入力行の最大長 */</span>
<span class="synType">int</span> main(<span class="synType">void</span>);
<span class="synType">int</span> main(<span class="synType">void</span>)
{
<span class="synType">char</span> buf[MAX_LINE];
<span class="synType">int</span> n;
printf (<span class="synConstant">&#34;現在の時刻(「時」だけでよい)を教えてください。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
gets(buf);
n = atoi(buf);
<span class="synStatement">if</span> (n &#60; <span class="synConstant"></span> || <span class="synConstant">24</span> &#60; n) {
printf (<span class="synConstant">&#34;Hour must be:</span><span class="synSpecial">\n</span><span class="synConstant"> 0 &#60;= hour &#60;= 24</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synStatement">else</span> <span class="synStatement">if</span> (<span class="synConstant"></span> &#60;= n &#38;&#38; n &#60;= <span class="synConstant">11</span>) {
printf (<span class="synConstant">&#34;おはようございます。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synStatement">else</span> <span class="synStatement">if</span> (n == <span class="synConstant">12</span>) {
printf (<span class="synConstant">&#34;お昼です。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synStatement">else</span> <span class="synStatement">if</span> (<span class="synConstant">13</span> &#60;= n &#38;&#38; n &#60;= <span class="synConstant">18</span>) {
printf (<span class="synConstant">&#34;こんにちわ。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synStatement">else</span> <span class="synStatement">if</span> (<span class="synConstant">19</span> &#60;= n &#38;&#38; n &#60;= <span class="synConstant">23</span>) {
printf (<span class="synConstant">&#34;こんばんわ。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synStatement">return</span>(<span class="synConstant"></span>);
}
</pre>
<p>
境界にあたる場合の条件に注意。自分の場合、「=」をつけ忘れていた。
</p>
<h4>
ここまでで Perl と違うと思った部分
</h4>
<ul>
<li>
必ず main から始まる
</li>
<li>
変数の方を最初に宣言しなければならない
</li>
<li>
Perl だとコンテクストに応じて様々な姿を変数はとるけれど、 C だと自分で型を変換しなければならない(→ atoi
</li>
<li>
C の char 型は一文字しか格納できない。だから配列として宣言して文字列を格納している…ようだ
</li>
</ul>
<p>
自分は Perl のコンテクストみたいな考えの方が好きかもしれない。
</p>
</div>