blog/content/post/2008/03/09/2008-03-09-『新版perl言語プログラミング...

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---
title: '『[新版Perl言語プログラミングレッスン入門編』第10章 サブルーチン'
author: kazu634
date: 2008-03-09
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categories:
- Perl
- Programming
---
<div class="section">
<p>
 今日はサブルーチンだよー。
</p>
<p>
<a name="seemore"></a>
</p>
<h4>
簡単なサブルーチン
</h4>
<pre class="syntax-highlight">
<span class="synStatement">use strict</span>;
<span class="synStatement">use warnings</span>;
<span class="synStatement">my</span> (<span class="synIdentifier">$x</span>, <span class="synIdentifier">$y</span>) = (<span class="synConstant">123</span>, <span class="synConstant">456</span>);
<span class="synIdentifier">&#38;print_xy</span>(<span class="synIdentifier">$x</span>, <span class="synIdentifier">$y</span>);
<span class="synStatement">sub</span><span class="synIdentifier"> print_xy </span>{
<span class="synStatement">my</span> (<span class="synIdentifier">$x</span>, <span class="synIdentifier">$y</span>) = <span class="synIdentifier">@_</span>;
<span class="synStatement">print</span> <span class="synConstant">&#34;</span><span class="synSpecial">\$</span><span class="synConstant">x = </span><span class="synIdentifier">$x</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>;
<span class="synStatement">print</span> <span class="synConstant">&#34;</span><span class="synSpecial">\$</span><span class="synConstant">y = </span><span class="synIdentifier">$y</span><span class="synSpecial">\n</span><span class="synConstant">&#34;</span>;
}
</pre>
<p>
&&#8230;」でサブルーチン呼び出しという意味になる。「@_」は引数のリストという意味かな
</p>
<h4>
戻り値のあるサブルーチン
</h4>
<p>
 戻り値のあるサブルーチンは、returnを用いると実現できるよ
</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;calc_ave</span>(<span class="synConstant">100</span>, <span class="synConstant">50</span>, <span class="synConstant">30</span>, <span class="synConstant">20</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_ave </span>{
<span class="synStatement">my</span> <span class="synIdentifier">@nums</span> = <span class="synIdentifier">@_</span>;
<span class="synStatement">my</span> <span class="synIdentifier">$sum</span>;
<span class="synStatement">foreach</span> (<span class="synIdentifier">@nums</span>) {
<span class="synIdentifier">$sum</span> = <span class="synIdentifier">$sum</span> + <span class="synIdentifier">$_</span>;
}
<span class="synStatement">my</span> <span class="synIdentifier">$ave</span> = <span class="synIdentifier">$sum</span> / <span class="synIdentifier">@nums</span>;
<span class="synStatement">return</span> <span class="synIdentifier">$ave</span>
}
</pre>
<p>
本に載っているやつだと汎用的じゃあなかったから、引数が何個でも大丈夫なようにしてみた。直前の章のコンテクストがうまく理解できている気がする( my $ave = $sum / @nums。この場合スカラーコンテクストだから、@numsは配列の要素数になるんだよね
</p>
</div>