blog/content/post/2008/08/05/2008-08-05-00000991.md

---
title: '８章: 真偽値と判断'
author: kazu634
date: 2008-08-05
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categories:
  - gauche
  - Lisp

---
<div class="section">
<p>
    勉強の続きだよ。
</p>

<p>
<a name="seemore"></a>
</p>

<h4>
    型を判定する手続き
</h4>

<ul>
<li>
      pair?
</li>
<li>
      null?
</li>
<li>
      list?
</li>
<li>
      boolean?
</li>
<li>
      symbol?
</li>
<li>
      number?
</li>
<li>
      char?
</li>
<li>
      string?
</li>
</ul>

<h4>
    性質を判定する手続き
</h4>

<ul>
<li>
      odd?
</li>
<li>
      even?
</li>
<li>
      zero?
</li>
<li>
      exact?
</li>
<li>
      char-alphabetic?
</li>
<li>
      proper-list?
</li>
</ul>

<h4>
    not
</h4>

<p>
    否定だよ。
</p>

<pre class="syntax-highlight">
gosh&#62; <span class="synSpecial">(</span><span class="synStatement">not</span> <span class="synSpecial">(</span><span class="synStatement">=</span> <span class="synConstant">2</span> <span class="synConstant">3</span><span class="synSpecial">))</span>
#<span class="synStatement">t</span>
gosh&#62; <span class="synSpecial">(</span><span class="synStatement">not</span> <span class="synSpecial">(</span><span class="synStatement">=</span> <span class="synConstant">2</span> <span class="synConstant">2</span><span class="synSpecial">))</span>
#f
</pre>

<h4>
    条件を判断するcase手続き
</h4>

<p>
    select caseなんかと同じみたいだ。
</p>

<pre class="syntax-highlight">
gosh&#62; <span class="synSpecial">(</span>define <span class="synSpecial">(</span>score card<span class="synSpecial">)</span>
<span class="synSpecial">(</span><span class="synStatement">case</span> card
<span class="synSpecial">((</span>A<span class="synSpecial">)</span> <span class="synConstant">11</span><span class="synSpecial">)</span>
<span class="synSpecial">((</span>J Q K<span class="synSpecial">)</span> <span class="synConstant">10</span><span class="synSpecial">)</span>
<span class="synSpecial">((</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="synConstant">7</span> <span class="synConstant">8</span> <span class="synConstant">9</span> <span class="synConstant">10</span><span class="synSpecial">)</span> card<span class="synSpecial">)))</span>
score
gosh&#62; <span class="synSpecial">(</span>score <span class="synConstant">4</span><span class="synSpecial">)</span>
<span class="synConstant">4</span>
gosh&#62; <span class="synSpecial">(</span>score <span class="synConstant">10</span><span class="synSpecial">)</span>
<span class="synConstant">10</span>
gosh&#62; <span class="synSpecial">(</span>score <span class="synSpecial">'</span><span class="synIdentifier">A</span><span class="synSpecial">)</span>
<span class="synConstant">11</span>
</pre>

<h4>
    条件が真の時だけ処理を行うwhen手続き
</h4>

<p>
    これだとif手続きの方がいいのかもしれないけど:
</p>

<pre class="syntax-highlight">
gosh&#62; <span class="synSpecial">(</span>define <span class="synSpecial">(</span>foo num<span class="synSpecial">)</span>
<span class="synSpecial">(</span><span class="synStatement">when</span> <span class="synSpecial">(</span><span class="synStatement">&#60;</span> num <span class="synConstant">10</span><span class="synSpecial">)</span>
num<span class="synSpecial">))</span>
foo
gosh&#62; <span class="synSpecial">(</span>foo <span class="synConstant">4</span><span class="synSpecial">)</span>
<span class="synConstant">4</span>
gosh&#62; <span class="synSpecial">(</span>foo <span class="synConstant">11</span><span class="synSpecial">)</span>
#&#60;undef&#62;
</pre>

<p>
    ちなみに条件式が偽のときだけ式を評価させたい場合はunlessを用いるよん。
</p>

<h4>
    1から任意の整数までの和を足しあわせた結果を表示
</h4>

<p>
    こんなんでいいのかー。すごく短い。
</p>

<pre class="syntax-highlight">
gosh&#62; <span class="synSpecial">(</span>define <span class="synSpecial">(</span>sum n<span class="synSpecial">)</span>
<span class="synSpecial">(</span><span class="synStatement">if</span> <span class="synSpecial">(</span><span class="synStatement">=</span> n <span class="synConstant">1</span><span class="synSpecial">)</span>
<span class="synConstant">1</span>
<span class="synSpecial">(</span><span class="synStatement">+</span> <span class="synSpecial">(</span>sum <span class="synSpecial">(</span><span class="synStatement">-</span> n <span class="synConstant">1</span><span class="synSpecial">))</span> n<span class="synSpecial">)))</span>
sum
gosh&#62; <span class="synSpecial">(</span>sum <span class="synConstant">10</span><span class="synSpecial">)</span>
<span class="synConstant">55</span>
</pre>

<p>
    Cだとこんな感じかしら？
</p>

<pre class="syntax-highlight">
<span class="synComment">/* ======================= */</span>
<span class="synComment">/* === Include library === */</span>
<span class="synComment">/* ======================= */</span>
<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="synComment">/* ============ */</span>
<span class="synComment">/* === main === */</span>
<span class="synComment">/* ============ */</span>
<span class="synType">int</span> main(<span class="synType">int</span> argc, <span class="synType">char</span> *argv[])
{
<span class="synType">int</span> i = <span class="synConstant"></span>;
<span class="synType">int</span> sum = <span class="synConstant"></span>;
<span class="synType">int</span> num = atoi(argv[<span class="synConstant">1</span>]);
<span class="synStatement">for</span> (i = <span class="synConstant"></span>; i &#60;= num; ++i)
{
sum += i;
}
printf(<span class="synConstant">&#34;</span><span class="synSpecial">%d\n</span><span class="synConstant">&#34;</span>, sum);
}
</pre>

<p>
    発想が全然違う気がする。
</p>

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