73 lines
5.5 KiB
Markdown
73 lines
5.5 KiB
Markdown
---
|
||
title: Ninety-nine Lisp Problems – P10の解答
|
||
author: kazu634
|
||
date: 2010-11-24
|
||
url: /2010/11/24/_1632/
|
||
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:5389;}s:9:"hash_tags";a:0:{}s:8:"accounts";a:1:{i:0;s:7:"kazu634";}}'
|
||
categories:
|
||
- gauche
|
||
- Lisp
|
||
|
||
---
|
||
<div class="section">
|
||
<p>
|
||
P9の解答で作成した関数を元にして、リスト空リストへの変換を行う形で解答を作成してみました。つまり
|
||
</p>
|
||
|
||
<ol>
|
||
<li>
|
||
packでリストを作成する
|
||
</li>
|
||
<li>
|
||
packで作られたリストの中のリストを変換する手続きencode-listを作成する
|
||
</li>
|
||
<li>
|
||
packに対してencode-listをmapする
|
||
</li>
|
||
</ol>
|
||
|
||
<p>
|
||
感じでやってみました。
|
||
</p>
|
||
|
||
<h4>
|
||
ソース
|
||
</h4>
|
||
|
||
<pre class="syntax-highlight">
|
||
<span class="synComment">;; P10 (*) Run-length encoding of a list.</span>
|
||
<span class="synComment">;; Use the result of problem P09 to implement the so-called run-length encoding data compression method. Consecutive duplicates of elements are encoded as lists (N E) where N is the number of duplicates of the element E.</span>
|
||
<span class="synComment">;; Example:</span>
|
||
<span class="synComment">;; * (encode '(a a a a b c c a a d e e e e))</span>
|
||
<span class="synComment">;; ((4 A) (1 B) (2 C) (2 A) (1 D)(4 E))</span>
|
||
<span class="synSpecial">(</span>define <span class="synSpecial">(</span>pack-seed front sublist result l<span class="synSpecial">)</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">cond</span>
|
||
[<span class="synSpecial">(</span><span class="synStatement">null</span>? l<span class="synSpecial">)</span> <span class="synSpecial">(</span><span class="synStatement">append</span> result <span class="synSpecial">(</span><span class="synStatement">list</span> sublist<span class="synSpecial">))</span>]
|
||
[<span class="synSpecial">(</span><span class="synStatement">eq</span>? front <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">))</span> <span class="synSpecial">(</span>pack-seed front
|
||
<span class="synSpecial">(</span><span class="synStatement">append</span> sublist
|
||
<span class="synSpecial">(</span><span class="synStatement">list</span> front<span class="synSpecial">))</span>
|
||
result
|
||
<span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">))</span>]
|
||
[else <span class="synSpecial">(</span>pack-seed <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">)</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">list</span> <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">))</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">if</span> <span class="synSpecial">(</span><span class="synStatement">null</span>? result<span class="synSpecial">)</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">if</span> <span class="synSpecial">(</span><span class="synStatement">null</span>? sublist<span class="synSpecial">)</span>
|
||
<span class="synSpecial">'()</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">append</span> result <span class="synSpecial">(</span><span class="synStatement">list</span> sublist<span class="synSpecial">)))</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">append</span> result <span class="synSpecial">(</span><span class="synStatement">list</span> sublist<span class="synSpecial">)))</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">))</span>]<span class="synSpecial">))</span>
|
||
<span class="synSpecial">(</span>define <span class="synSpecial">(</span>pack l<span class="synSpecial">)</span>
|
||
<span class="synSpecial">(</span>pack-seed #f <span class="synSpecial">'()</span> <span class="synSpecial">'()</span> l<span class="synSpecial">))</span>
|
||
<span class="synSpecial">(</span>define <span class="synSpecial">(</span>encode-list l<span class="synSpecial">)</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">let</span> <span class="synSpecial">((</span>num <span class="synSpecial">(</span><span class="synStatement">length</span> l<span class="synSpecial">)))</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">append</span> <span class="synSpecial">(</span><span class="synStatement">list</span> num<span class="synSpecial">)</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">list</span> <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">)))))</span>
|
||
<span class="synSpecial">(</span>encode-list <span class="synSpecial">'(</span>a a a a a<span class="synSpecial">))</span>
|
||
<span class="synSpecial">(</span>define <span class="synSpecial">(</span>encode l<span class="synSpecial">)</span>
|
||
<span class="synSpecial">(</span><span class="synStatement">map</span> <span class="synSpecial">(</span><span class="synStatement">lambda</span> <span class="synSpecial">(</span>l<span class="synSpecial">)</span>
|
||
<span class="synSpecial">(</span>encode-list l<span class="synSpecial">))</span>
|
||
<span class="synSpecial">(</span>pack l<span class="synSpecial">)))</span>
|
||
<span class="synSpecial">(</span>encode <span class="synSpecial">'(</span>a a a a b c c a a d e e e e<span class="synSpecial">))</span>
|
||
</pre>
|
||
</div> |