57 lines
5.6 KiB
Markdown
57 lines
5.6 KiB
Markdown
---
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title: 'Lispの問題 from 「L-99: Ninety-Nine Lisp Problems」'
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author: kazu634
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date: 2010-09-05
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wordtwit_post_info:
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- '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:5339;}s:9:"hash_tags";a:0:{}s:8:"accounts";a:1:{i:0;s:7:"kazu634";}}'
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categories:
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- gauche
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- Lisp
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---
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<div class="section">
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<p>
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またまた頑張ってみました。letrecを使って、結果を渡しながらやっている。もしかしたら、継続で書き換えられる？
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</p>
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<pre class="syntax-highlight">
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<span class="synComment">;; P07 (**) Flatten a nested list structure.</span>
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<span class="synComment">;; Transform a list, possibly holding lists as elements into a `flat' list by replacing each list with its elements (recursively).</span>
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<span class="synComment">;; Example:</span>
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<span class="synComment">;; * (my-flatten '(a (b (c d) e)))</span>
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<span class="synComment">;; (A B C D E)</span>
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<span class="synComment">;; Hint: Use the predefined functions list and append.</span>
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<span class="synSpecial">(</span>define <span class="synSpecial">(</span><span class="synStatement">atom</span>? l<span class="synSpecial">)</span>
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<span class="synSpecial">(</span><span class="synStatement">and</span> <span class="synSpecial">(</span><span class="synStatement">not</span> <span class="synSpecial">(</span>pair? l<span class="synSpecial">))</span>
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<span class="synSpecial">(</span><span class="synStatement">not</span> <span class="synSpecial">(</span><span class="synStatement">null</span>? l<span class="synSpecial">))))</span>
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<span class="synSpecial">(</span>define <span class="synSpecial">(</span>my-flatten l<span class="synSpecial">)</span>
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<span class="synSpecial">(</span>letrec <span class="synSpecial">((</span>temp <span class="synSpecial">(</span><span class="synStatement">lambda</span> <span class="synSpecial">(</span>result l<span class="synSpecial">)</span>
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<span class="synSpecial">(</span><span class="synStatement">cond</span>
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[<span class="synSpecial">(</span><span class="synStatement">null</span>? l<span class="synSpecial">)</span> result]
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[<span class="synSpecial">(</span><span class="synStatement">atom</span>? <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">))</span> <span class="synSpecial">(</span>temp <span class="synSpecial">(</span><span class="synStatement">append</span> result
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<span class="synSpecial">(</span><span class="synStatement">list</span> <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">)))</span>
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<span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">))</span>]
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[else <span class="synSpecial">(</span>temp <span class="synSpecial">(</span>temp result <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">))</span>
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<span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">))</span>]<span class="synSpecial">))))</span>
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<span class="synSpecial">(</span>temp <span class="synSpecial">'()</span> l<span class="synSpecial">)))</span>
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<span class="synSpecial">(</span>my-flatten <span class="synSpecial">'(</span>a <span class="synSpecial">(</span>b <span class="synSpecial">(</span>c d<span class="synSpecial">)</span> e<span class="synSpecial">)))</span>
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<span class="synComment">;; P08 (**) Eliminate consecutive duplicates of list elements.</span>
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<span class="synComment">;; If a list contains repeated elements they should be replaced with a single copy of the element. The order of the elements should not be changed.</span>
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<span class="synComment">;; Example:</span>
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<span class="synComment">;; * (compress '(a a a a b c c a a d e e e e))</span>
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<span class="synComment">;; (A B C A D E)</span>
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<span class="synSpecial">(</span>define <span class="synSpecial">(</span>compress l<span class="synSpecial">)</span>
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<span class="synSpecial">(</span>letrec <span class="synSpecial">((</span>temp <span class="synSpecial">(</span><span class="synStatement">lambda</span> <span class="synSpecial">(</span>front result l<span class="synSpecial">)</span>
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<span class="synSpecial">(</span><span class="synStatement">cond</span>
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[<span class="synSpecial">(</span><span class="synStatement">null</span>? l<span class="synSpecial">)</span> result]
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[<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>temp front
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result
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<span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">))</span>]
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[else <span class="synSpecial">(</span>temp <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">)</span>
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<span class="synSpecial">(</span><span class="synStatement">append</span> result <span class="synSpecial">(</span><span class="synStatement">list</span> <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">)))</span>
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<span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">))</span>]<span class="synSpecial">))))</span>
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<span class="synSpecial">(</span>temp <span class="synSpecial">'()</span> <span class="synSpecial">'()</span> l<span class="synSpecial">)))</span>
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<span class="synSpecial">(</span>compress <span class="synSpecial">'(</span>a a a a b c c a a d e e e e<span class="synSpecial">))</span>
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</pre>
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</div>
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