kazu634
/
blog
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
blog/content/post/2008-05-01-00000901.md

208 lines
11 KiB
Markdown
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

---
title: 『新版C言語プログラミングレッスン 入門編』第８章・関数
author: kazu634
date: 2008-05-01
url: /2008/05/01/_967/
wordtwit_post_info:
- 'O:8:"stdClass":13:{s:6:"manual";b:0;s:11:"tweet_times";i:1;s:5:"delay";i:0;s:7:"enabled";i:1;s:10:"separation";s:2:"60";s:7:"version";s:3:"3.7";s:14:"tweet_template";b:0;s:6:"status";i:2;s:6:"result";a:0:{}s:13:"tweet_counter";i:2;s:13:"tweet_log_ids";a:1:{i:0;i:3961;}s:9:"hash_tags";a:0:{}s:8:"accounts";a:1:{i:0;s:7:"kazu634";}}'
categories:
- C
- Programming
---
<div class="section">
<h4>
関数の定義
</h4>
<p>
　Cの関数は
</p>
<blockquote title="http" cite="http://www.amazon.co.jp/%E6%96%B0%E7%89%88C%E8%A8%80%E8%AA%9E%E3%83%97%E3%83%AD%E3%82%B0%E3%83%A9%E3%83%9F%E3%83%B3%E3%82%B0%E3%83%AC%E3%83%83%E3%82%B9%E3%83%B3-%E5%85%A5%E9%96%80%E7%B7%A8-%E7%B5%90%E5%9F%8E%E6%B5%A9/dp/4797336781/ref=sr_1_10?ie=UTF8&s=books&qid=1209639049&sr=1-10">
<p>
0個以上の引数を持ち、0個か1個の戻り値を持ち、まとまった仕事を行うプラグラムの一部分」
</p>
<p>
<cite><a href="http://www.amazon.co.jp/%E6%96%B0%E7%89%88C%E8%A8%80%E8%AA%9E%E3%83%97%E3%83%AD%E3%82%B0%E3%83%A9%E3%83%9F%E3%83%B3%E3%82%B0%E3%83%AC%E3%83%83%E3%82%B9%E3%83%B3-%E5%85%A5%E9%96%80%E7%B7%A8-%E7%B5%90%E5%9F%8E%E6%B5%A9/dp/4797336781/ref=sr_1_10?ie=UTF8&s=books&qid=1209639049&sr=1-10" onclick="__gaTracker('send', 'event', 'outbound-article', 'http://www.amazon.co.jp/%E6%96%B0%E7%89%88C%E8%A8%80%E8%AA%9E%E3%83%97%E3%83%AD%E3%82%B0%E3%83%A9%E3%83%9F%E3%83%B3%E3%82%B0%E3%83%AC%E3%83%83%E3%82%B9%E3%83%B3-%E5%85%A5%E9%96%80%E7%B7%A8-%E7%B5%90%E5%9F%8E%E6%B5%A9/dp/4797336781/ref=sr_1_10?ie=UTF8&s=books&qid=1209639049&sr=1-10', 'http://www.amazon.co.jp/%E6%96%B0%E7%89%88C%E8%A8%80%E8%AA%9E%E3%83%97%E3%83%AD%E3%82%B0%E3%83%A9%E3%83%9F%E3%83%B3%E3%82%B0%E3%83%AC%E3%83%83%E3%82%B9%E3%83%B3-%E5%85%A5%E9%96%80%E7%B7%A8-%E7%B5%90%E5%9F%8E%E6%B5%A9/dp/4797336781/ref=sr_1_10?ie=UTF8&#038;s=books&#038;qid=1209639049&#038;sr=1-10:title');" target="_blank">http://www.amazon.co.jp/%E6%96%B0%E7%89%88C%E8%A8%80%E8%AA%9E%E3%83%97%E3%83%AD%E3%82%B0%E3%83%A9%E3%83%9F%E3%83%B3%E3%82%B0%E3%83%AC%E3%83%83%E3%82%B9%E3%83%B3-%E5%85%A5%E9%96%80%E7%B7%A8-%E7%B5%90%E5%9F%8E%E6%B5%A9/dp/4797336781/ref=sr_1_10?ie=UTF8&s=books&qid=1209639049&sr=1-10:title</a></cite>
</p>
</blockquote>
<p>
<a name="seemore"></a>
</p>
<h4>
3割引の計算をする関数
</h4>
<pre class="syntax-highlight">
<span class="synPreProc">#include </span><span class="synConstant">&#60;stdio.h&#62;</span>
<span class="synType">float</span> calc(<span class="synType">float</span> x);
<span class="synType">int</span> main(<span class="synType">void</span>);
<span class="synComment">/* この部分が関数だよ */</span>
<span class="synType">float</span> calc(<span class="synType">float</span> x)
{
<span class="synStatement">return</span>(x * <span class="synConstant">0.7</span>);
}
<span class="synType">int</span> main(<span class="synType">void</span>)
{
<span class="synType">float</span> y;
y = calc(<span class="synConstant">10000.0</span>);
printf (<span class="synConstant">&#34;値段 </span><span class="synSpecial">%.0f</span><span class="synConstant"> 円の時&#34;</span>, <span class="synConstant">10000.0</span>);
printf (<span class="synConstant">&#34;</span><span class="synSpecial">%.0f</span><span class="synConstant"> 円支払います。</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>, y);
<span class="synStatement">return</span>(<span class="synConstant"></span>);
}
</pre>
<p>
ちなみに Perl だと、こんな感じかな？
</p>
<pre class="syntax-highlight">
<span class="synStatement">use strict</span>;
<span class="synStatement">use warnings</span>;
<span class="synStatement">my</span> <span class="synIdentifier">$sum</span> = <span class="synConstant">10000</span>;
<span class="synIdentifier">$sum</span> = <span class="synIdentifier">&#38;calc</span>(<span class="synIdentifier">$sum</span>);
<span class="synStatement">print</span> <span class="synIdentifier">$sum</span>, <span class="synConstant">&#34;</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>;
<span class="synStatement">sub</span><span class="synIdentifier"> calc</span>{
<span class="synStatement">my</span> <span class="synIdentifier">$i</span>;
<span class="synStatement">my</span> <span class="synIdentifier">@nums</span> = <span class="synIdentifier">@_</span>;
<span class="synIdentifier">$i</span> = <span class="synIdentifier">$nums</span>[<span class="synConstant"></span>] * <span class="synConstant">0.7</span>;
<span class="synStatement">return</span> <span class="synIdentifier">$i</span>;
}
</pre>
<p>
Cだと変数の方の宣言をする必要があって、結構がちがちにやる必要があります。それに対して、Perlだと引数の個数を指定する必要がなかったりと自由度高め。自分は配列の1番目（添え字0）に決めうちで計算をさせています。Perlの自由度は高いなー。
</p>
<p>
</p>
<h4>
戻り値のない関数
</h4>
<p>
　アスタリスクをn個表示させます。
</p>
<pre class="syntax-highlight">
<span class="synPreProc">#include </span><span class="synConstant">&#60;stdio.h&#62;</span>
<span class="synType">void</span> prt_graph(<span class="synType">int</span> x);
<span class="synType">int</span> main(<span class="synType">void</span>);
<span class="synType">void</span> prt_graph(<span class="synType">int</span> x)
{
<span class="synType">int</span> i;
<span class="synStatement">for</span> (i = <span class="synConstant"></span>;i &#60; x;i++) {
printf (<span class="synConstant">&#34;*&#34;</span>);
}
printf (<span class="synConstant">&#34;</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synType">int</span> main(<span class="synType">void</span>)
{
prt_graph(<span class="synConstant">10</span>);
<span class="synStatement">return</span>(<span class="synConstant"></span>);
}
</pre>
<p>
Perlだと、こんな感じになる。簡単だ。
</p>
<pre class="syntax-highlight">
<span class="synStatement">use strict</span>;
<span class="synStatement">use warnings</span>;
<span class="synStatement">print</span> <span class="synConstant">&#34;*&#34;</span> x <span class="synConstant">10</span>;
<span class="synStatement">print</span> <span class="synConstant">&#34;</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>;
</pre>
<h4>
xのn乗を計算する
</h4>
<pre class="syntax-highlight">
<span class="synPreProc">#include </span><span class="synConstant">&#60;stdio.h&#62;</span>
<span class="synType">int</span> get_power(<span class="synType">int</span> x, <span class="synType">int</span> n);
<span class="synType">int</span> main(<span class="synType">void</span>);
<span class="synType">int</span> get_power(<span class="synType">int</span> x, <span class="synType">int</span> n)
{
<span class="synComment">/* 変数の定義 */</span>
<span class="synComment">/* i はカウンタ */</span>
<span class="synComment">/* res は計算と戻り値のため */</span>
<span class="synType">int</span> i;
<span class="synType">int</span> res = <span class="synConstant">1</span>;
<span class="synStatement">for</span> (i = <span class="synConstant"></span>;i &#60;= n - <span class="synConstant">1</span>;i++) {
res = res * x;
}
<span class="synStatement">return</span>(res);
}
<span class="synType">int</span> main(<span class="synType">void</span>)
{
<span class="synType">int</span> temp;
temp = get_power(<span class="synConstant">7</span>, <span class="synConstant">4</span>);
printf (<span class="synConstant">&#34;</span><span class="synSpecial">%d</span><span class="synConstant">&#34;</span>, temp);
printf (<span class="synConstant">&#34;</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
<span class="synStatement">return</span>(<span class="synConstant"></span>);
}
</pre>
<p>
Perlだとこうなる。ただし、厳密な引数のチェックはしていない。
</p>
<pre class="syntax-highlight">
<span class="synStatement">use strict</span>;
<span class="synStatement">use warnings</span>;
<span class="synStatement">print</span> <span class="synIdentifier">&#38;get_power</span>(<span class="synConstant">10</span>,<span class="synConstant">3</span>);
<span class="synStatement">print</span> <span class="synConstant">&#34;</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>;
<span class="synStatement">sub</span><span class="synIdentifier"> get_power</span>{
<span class="synStatement">my</span> <span class="synIdentifier">$res</span> = <span class="synConstant">1</span>;
<span class="synStatement">my</span> (<span class="synIdentifier">$x</span>, <span class="synIdentifier">$n</span>) = <span class="synIdentifier">@_</span>;
<span class="synStatement">for</span> (<span class="synStatement">my</span> <span class="synIdentifier">$i</span> = <span class="synConstant"></span>; <span class="synIdentifier">$i</span> &#60;= <span class="synIdentifier">$n</span> - <span class="synConstant">1</span>; <span class="synIdentifier">$i</span>++) {
<span class="synIdentifier">$res</span> = <span class="synIdentifier">$res</span> * <span class="synIdentifier">$x</span>;
}
<span class="synStatement">return</span> <span class="synIdentifier">$res</span>;
}
</pre>
<h4>
練習問題
</h4>
<p>
　nの2乗個の*を表示させる（nを10→0→10と変化させる）。
</p>
<pre class="syntax-highlight">
<span class="synPreProc">#include </span><span class="synConstant">&#60;stdio.h&#62;</span>
<span class="synComment">/* プロトタイプ宣言 */</span>
<span class="synType">void</span> prt_graph(<span class="synType">int</span> n);
<span class="synType">int</span> main(<span class="synType">void</span>);
<span class="synComment">/* 関数 prt_graph */</span>
<span class="synType">void</span> prt_graph(<span class="synType">int</span> n)
{
<span class="synType">int</span> i;
<span class="synType">int</span> cnt;
cnt = n * n;
<span class="synStatement">for</span> (i = <span class="synConstant"></span>;i &#60; cnt;i++) {
printf (<span class="synConstant">&#34;*&#34;</span>);
}
printf (<span class="synConstant">&#34;</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>);
}
<span class="synComment">/* メイン */</span>
<span class="synType">int</span> main(<span class="synType">void</span>)
{
<span class="synType">int</span> i;
<span class="synStatement">for</span> (i = <span class="synConstant">10</span>;<span class="synConstant"></span> &#60; i;i = i -<span class="synConstant">1</span>) {
prt_graph(i);
}
<span class="synStatement">for</span> (i = <span class="synConstant"></span>;i &#60; <span class="synConstant">11</span>; i++) {
prt_graph(i);
}
<span class="synStatement">return</span>(<span class="synConstant"></span>);
}
</pre>
</div>
Reference in New Issue View Git Blame Copy Permalink