61 lines
5.6 KiB
Markdown
61 lines
5.6 KiB
Markdown
---
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title: 'Lispの問題 1～3 from L-99: Ninety-Nine Lisp Problems'
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author: kazu634
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date: 2010-08-29
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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:5333;}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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「<a href="http://www.ic.unicamp.br/~meidanis/courses/mc336/2006s2/funcional/L-99_Ninety-Nine_Lisp_Problems.html" onclick="__gaTracker('send', 'event', 'outbound-article', 'http://www.ic.unicamp.br/~meidanis/courses/mc336/2006s2/funcional/L-99_Ninety-Nine_Lisp_Problems.html', 'L-99: Ninety-Nine Lisp Problems');" target="_blank">L-99: Ninety-Nine Lisp Problems</a>」で掲載されている問題を解いてみました。この辺なら問題なさそう。
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</p>
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<p>
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番号が増えていくと、手に負えなくなりそうだなぁ。。。
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</p>
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<pre class="syntax-highlight">
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<span class="synComment">;; P01 (*) Find the last box of a list.</span>
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<span class="synComment">;; Example:</span>
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<span class="synComment">;; * (my-last '(a b c d))</span>
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<span class="synComment">;; (D)</span>
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<span class="synSpecial">(</span>define <span class="synSpecial">(</span>my-last l<span class="synSpecial">)</span>
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<span class="synSpecial">(</span>letrec <span class="synSpecial">((</span>temporary <span class="synSpecial">(</span><span class="synStatement">lambda</span> <span class="synSpecial">(</span>a 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> a]
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[else <span class="synSpecial">(</span>temporary <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">)</span> <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>temporary <span class="synSpecial">'()</span> l<span class="synSpecial">)))</span>
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<span class="synSpecial">(</span>my-last <span class="synSpecial">'(</span>a b c d<span class="synSpecial">))</span>
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<span class="synComment">;; P02 (*) Find the last but one box of a list.</span>
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<span class="synComment">;; Example:</span>
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<span class="synComment">;; * (my-but-last '(a b c d))</span>
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<span class="synComment">;; (C D)</span>
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<span class="synSpecial">(</span>define <span class="synSpecial">(</span>my-but-last 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> <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><span class="synStatement">null</span>? <span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">)))</span>
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<span class="synSpecial">(</span><span class="synStatement">null</span>? <span class="synSpecial">(</span><span class="synStatement">cdr</span> <span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">))))</span> l]
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[else <span class="synSpecial">(</span>my-but-last <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>my-but-last <span class="synSpecial">'(</span>a b c d e f g<span class="synSpecial">))</span>
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<span class="synComment">;; P03 (*) Find the K'th element of a list.</span>
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<span class="synComment">;; The first element in the list is number 1.</span>
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<span class="synComment">;; Example:</span>
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<span class="synComment">;; * (element-at '(a b c d e) 3)</span>
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<span class="synComment">;; C</span>
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<span class="synSpecial">(</span>define <span class="synSpecial">(</span>element-at l index<span class="synSpecial">)</span>
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<span class="synSpecial">(</span>letrec <span class="synSpecial">((</span>temporary <span class="synSpecial">(</span><span class="synStatement">lambda</span> <span class="synSpecial">(</span>l index <span class="synStatement">count</span><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> <span class="synSpecial">'()</span>]
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[<span class="synSpecial">(</span><span class="synStatement">eq</span>? index <span class="synStatement">count</span><span class="synSpecial">)</span> <span class="synSpecial">(</span><span class="synStatement">car</span> l<span class="synSpecial">)</span>]
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[else <span class="synSpecial">(</span>temporary <span class="synSpecial">(</span><span class="synStatement">cdr</span> l<span class="synSpecial">)</span>
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index
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<span class="synSpecial">(</span><span class="synStatement">+</span> <span class="synStatement">count</span> <span class="synConstant">1</span><span class="synSpecial">))</span>]<span class="synSpecial">))))</span>
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<span class="synSpecial">(</span>temporary l index <span class="synConstant">1</span><span class="synSpecial">)))</span>
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<span class="synSpecial">(</span>element-at <span class="synSpecial">'(</span>a b c d e<span class="synSpecial">)</span> <span class="synConstant">-1</span><span class="synSpecial">)</span>
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</pre>
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</div>
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