blog/content/post/2008-08-28-00001013.md

---
title: 手続き中の引数の書き方がわからないかもしれない
author: kazu634
date: 2008-08-28
url: /2008/08/28/_1089/
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categories:
  - gauche
  - Lisp

---
<div class="section">
<p>
    『<a href="http://d.hatena.ne.jp/asin/4873113482" onclick="__gaTracker('send', 'event', 'outbound-article', 'http://d.hatena.ne.jp/asin/4873113482', 'プログラミングGauche');">プログラミングGauche</a>』を再度読み直しているところ。わかっていないところが多い。とりあえず手続き中の引数の書き方はオーソドックスなのは次の二つのパターン:
</p>

<pre class="syntax-highlight">
<span class="synSpecial">(</span>define plus2_1
<span class="synSpecial">(</span><span class="synStatement">lambda</span> <span class="synSpecial">(</span>arg<span class="synSpecial">)</span> <span class="synSpecial">(</span><span class="synStatement">+</span> arg <span class="synConstant">2</span><span class="synSpecial">)))</span>
<span class="synSpecial">(</span>define <span class="synSpecial">(</span>plus2_2 arg<span class="synSpecial">)</span>
<span class="synSpecial">(</span><span class="synStatement">+</span> arg <span class="synConstant">2</span><span class="synSpecial">))</span>
</pre>

<p>
    こう宣言することで
</p>

<pre class="syntax-highlight">
gosh&#62; <span class="synSpecial">(</span>plus2_1 <span class="synConstant">5</span><span class="synSpecial">)</span>
<span class="synConstant">7</span>
gosh&#62; <span class="synSpecial">(</span>plus2_2 <span class="synConstant">5</span><span class="synSpecial">)</span>
<span class="synConstant">7</span>
</pre>

<p>
    となる。ここで76-7ページあたりの記述を見てみる。「受け取った引数を出力してから、任意の手続きを実行する手続き」としてmake-loggerが紹介されている。
</p>

<pre class="syntax-highlight">
<span class="synSpecial">(</span>define <span class="synSpecial">(</span>make_logger func<span class="synSpecial">)</span>
<span class="synSpecial">(</span><span class="synStatement">lambda</span> args
<span class="synSpecial">(</span><span class="synStatement">print</span> <span class="synConstant">&#34;args=&#34;</span> args<span class="synSpecial">)</span>
<span class="synSpecial">(</span><span class="synStatement">apply</span> func args<span class="synSpecial">)))</span>
<span class="synSpecial">(</span>define my_append_log <span class="synSpecial">(</span>make_logger <span class="synStatement">append</span><span class="synSpecial">))</span>
</pre>

<p>
    自分の理解だとこのmake_loggerは「(make_logger 手続き名 引数」とかが十分通用しそうに思っていた。けど、「引数は一つだ！」と怒られる。
</p>

<pre class="syntax-highlight">
gosh&#62; <span class="synSpecial">(</span>make_logger <span class="synStatement">print</span> <span class="synSpecial">'(</span>1 2 3<span class="synSpecial">))</span>
<span class="synStatement">***</span> ERROR: wrong <span class="synStatement">number</span> of arguments for #&#60;closure make_logger&#62; <span class="synSpecial">(</span>required <span class="synConstant">1</span>, got <span class="synConstant">2</span><span class="synSpecial">)</span>
Stack Trace:
_______________________________________
gosh&#62; <span class="synSpecial">(</span>make_logger <span class="synStatement">append</span> <span class="synSpecial">'(</span>1 2 3<span class="synSpecial">)</span> <span class="synSpecial">'(</span>1 2 3<span class="synSpecial">))</span>
<span class="synStatement">***</span> ERROR: wrong <span class="synStatement">number</span> of arguments for #&#60;closure make_logger&#62; <span class="synSpecial">(</span>required <span class="synConstant">1</span>, got <span class="synConstant">3</span><span class="synSpecial">)</span>
Stack Trace:
_______________________________________
gosh&#62; <span class="synSpecial">(</span>make_logger <span class="synStatement">append</span><span class="synSpecial">)</span>
#&#60;closure <span class="synSpecial">(</span>make_logger make_logger<span class="synSpecial">)</span><span class="synStatement">&#62;</span>
gosh&#62; <span class="synSpecial">(</span>make_logger<span class="synSpecial">)</span>
<span class="synStatement">***</span> ERROR: wrong <span class="synStatement">number</span> of arguments for #&#60;closure make_logger&#62; <span class="synSpecial">(</span>required <span class="synConstant">1</span>, got <span class="synConstant"></span><span class="synSpecial">)</span>
Stack Trace:
_______________________________________
</pre>

<p>
    うでも、これは大丈夫。
</p>

<pre class="syntax-highlight">
gosh&#62; <span class="synSpecial">(</span>my_append_log <span class="synSpecial">'(</span>1 2 3<span class="synSpecial">)</span> <span class="synSpecial">'(</span>4 5 6<span class="synSpecial">))</span>
args=<span class="synSpecial">((</span><span class="synConstant">1</span> <span class="synConstant">2</span> <span class="synConstant">3</span><span class="synSpecial">)</span> <span class="synSpecial">(</span><span class="synConstant">4</span> <span class="synConstant">5</span> <span class="synConstant">6</span><span class="synSpecial">))</span>
<span class="synSpecial">(</span><span class="synConstant">1</span> <span class="synConstant">2</span> <span class="synConstant">3</span> <span class="synConstant">4</span> <span class="synConstant">5</span> <span class="synConstant">6</span><span class="synSpecial">)</span>
</pre>

<p>
    (make_logger)の宣言中のlambdaはどこに消えたの？というか引数は一つだけでは？なんで複数個の引数がありなわけ？
</p>
</div>