--- title: applyの使い方がわかったかもしれない! author: kazu634 date: 2008-10-02 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:4321;}s:9:"hash_tags";a:0:{}s:8:"accounts";a:1:{i:0;s:7:"kazu634";}}' categories: - gauche - Lisp --- <div class="section"> <p> <a href="http://d.hatena.ne.jp/SaitoAtsushi/" onclick="__gaTracker('send', 'event', 'outbound-article', 'http://d.hatena.ne.jp/SaitoAtsushi/', 'id:SaitoAtsushi');">id:SaitoAtsushi</a>さんとShiroさんに教えていただいて、なんとなくわかった瞬間がきました!とりあえずその全過程をご覧ください。 </p> <pre class="syntax-highlight"> gosh> <span class="synSpecial">(</span><span class="synStatement">cons</span> <span class="synConstant">1</span> <span class="synConstant">2</span><span class="synSpecial">)</span> <span class="synSpecial">(</span><span class="synConstant">1</span><span class="synStatement"> . </span><span class="synConstant">2</span><span class="synSpecial">)</span> gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> <span class="synStatement">cons</span> <span class="synSpecial">'(</span>1 2<span class="synSpecial">))</span> <span class="synSpecial">(</span><span class="synConstant">1</span><span class="synStatement"> . </span><span class="synConstant">2</span><span class="synSpecial">)</span> gosh> <span class="synSpecial">(</span>define p <span class="synSpecial">'(</span>a b c<span class="synSpecial">))</span> p gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> <span class="synStatement">car</span> <span class="synSpecial">(</span><span class="synStatement">list</span> p<span class="synSpecial">))</span> a gosh> <span class="synSpecial">(</span><span class="synStatement">car</span> p<span class="synSpecial">)</span> a gosh> <span class="synSpecial">(</span><span class="synStatement">car</span> <span class="synSpecial">(</span><span class="synStatement">list</span> p<span class="synSpecial">))</span> <span class="synSpecial">(</span>a b c<span class="synSpecial">)</span> gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> <span class="synStatement">cdr</span> <span class="synSpecial">(</span><span class="synStatement">list</span> p<span class="synSpecial">))</span> <span class="synSpecial">(</span>b c<span class="synSpecial">)</span> </pre> <p> ここら辺の段階ではまだよくわかっていない。。。 </p> <pre class="syntax-highlight"> gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> list-ref <span class="synSpecial">(</span><span class="synStatement">list</span> p <span class="synConstant"></span><span class="synSpecial">))</span> a gosh> <span class="synSpecial">(</span>list-ref p <span class="synConstant"></span><span class="synSpecial">)</span> a gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> list-ref <span class="synSpecial">(</span><span class="synStatement">list</span> p <span class="synConstant">1</span><span class="synSpecial">))</span> b gosh> <span class="synSpecial">(</span>list-ref p <span class="synConstant">1</span><span class="synSpecial">)</span> b gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> list-ref <span class="synSpecial">(</span><span class="synStatement">list</span> p <span class="synConstant">2</span><span class="synSpecial">))</span> c gosh> <span class="synSpecial">(</span>list-ref p <span class="synConstant">2</span><span class="synSpecial">)</span> c gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> <span class="synStatement">length</span> <span class="synSpecial">(</span><span class="synStatement">list</span> p<span class="synSpecial">))</span> <span class="synConstant">3</span> gosh> <span class="synSpecial">(</span><span class="synStatement">length</span> p<span class="synSpecial">)</span> <span class="synConstant">3</span> gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> list-ref <span class="synSpecial">'(</span>1<span class="synSpecial">))</span> <span class="synStatement">***</span> ERROR: wrong <span class="synStatement">number</span> of arguments for #<subr list-ref> <span class="synSpecial">(</span>required <span class="synConstant">2</span>, got <span class="synConstant">1</span><span class="synSpecial">)</span> Stack Trace: _______________________________________ gosh> <span class="synSpecial">(</span><span class="synStatement">list</span> p <span class="synConstant">2</span><span class="synSpecial">)</span> <span class="synSpecial">((</span>a b c<span class="synSpecial">)</span> <span class="synConstant">2</span><span class="synSpecial">)</span> </pre> <p> ここら辺でもまだ事の重要性に気づいていなかった。。。 </p> <pre class="syntax-highlight"> gosh> <span class="synSpecial">(</span>list-ref p <span class="synConstant">1</span><span class="synSpecial">)</span> b gosh> <span class="synSpecial">(</span><span class="synStatement">list</span> p <span class="synConstant"></span><span class="synSpecial">)</span> <span class="synSpecial">((</span>a b c<span class="synSpecial">)</span> <span class="synConstant"></span><span class="synSpecial">)</span> </pre> <p> もしや…applyって「一番外側の()を外して手続きに引数として渡している」んじゃあ…そうじゃないと、 </p> <pre class="syntax-highlight"> gosh> <span class="synSpecial">(</span><span class="synStatement">apply</span> list-ref <span class="synSpecial">(</span><span class="synStatement">list</span> p <span class="synConstant">2</span><span class="synSpecial">))</span> c </pre> <p> とかになる理由が理解できない。これは結局 </p> <pre class="syntax-highlight"> <span class="synSpecial">(</span>list-ref <span class="synSpecial">'(</span>a b c<span class="synSpecial">)</span> <span class="synConstant"></span><span class="synSpecial">)</span> </pre> <p> となっているはず。そうじゃなければ、こんな挙動になるはずがない。。。 </p> <p> </p> <p> Shiro様、ありがとうございました(__)理解できました。 </p> </div>