2019-03-31 11:00:21 +00:00
---
title: 高階関数の練習をするよ
author: kazu634
date: 2008-10-09
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categories:
- gauche
- Lisp
---
< div class = "section" >
< p >
ちょっと前に自分なりにmaxを定義してみました。同じようにすれば、minも定義できます。
< / p >
< pre class = "syntax-highlight" >
< span class = "synSpecial" > (< / span > define < span class = "synSpecial" > (< / span > max-number lis< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > fold
< span class = "synSpecial" > (< / span > < span class = "synStatement" > lambda< / span > < span class = "synSpecial" > (< / span > a b< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > < span class = "synStatement" > if< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > < < / span > a b< span class = "synSpecial" > )< / span >
b
a< span class = "synSpecial" > ))< / span >
< span class = "synSpecial" > (< / span > < span class = "synStatement" > car< / span > lis< span class = "synSpecial" > )< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > cdr< / span > lis< span class = "synSpecial" > )))< / span >
< span class = "synSpecial" > (< / span > define < span class = "synSpecial" > (< / span > my_max< span class = "synStatement" > . < / span > args< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > max-number args< span class = "synSpecial" > ))< / span >
< span class = "synSpecial" > (< / span > define < span class = "synSpecial" > (< / span > min-number lis< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > fold
< span class = "synSpecial" > (< / span > < span class = "synStatement" > lambda< / span > < span class = "synSpecial" > (< / span > a b< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > < span class = "synStatement" > if< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > > < / span > a b< span class = "synSpecial" > )< / span >
b
a< span class = "synSpecial" > ))< / span >
< span class = "synSpecial" > (< / span > < span class = "synStatement" > car< / span > lis< span class = "synSpecial" > )< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > cdr< / span > lis< span class = "synSpecial" > )))< / span >
< span class = "synSpecial" > (< / span > define < span class = "synSpecial" > (< / span > my_min< span class = "synStatement" > . < / span > args< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > min-number args< span class = "synSpecial" > ))< / span >
< / pre >
< p >
この中から共通の構造を抜き出して、中間的な手続きを作成してみます。この中間的な手続きは「< 」や「>」を受け取って、「引数を一つ取る手続き」を戻り値とします。
< / p >
< pre class = "syntax-highlight" >
< span class = "synSpecial" > (< / span > define < span class = "synSpecial" > (< / span > pickup proc< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > < span class = "synStatement" > lambda< / span > < span class = "synSpecial" > (< / span > lis< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > fold
< span class = "synSpecial" > (< / span > < span class = "synStatement" > lambda< / span > < span class = "synSpecial" > (< / span > a b< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > (< / span > < span class = "synStatement" > if< / span > < span class = "synSpecial" > (< / span > proc a b< span class = "synSpecial" > )< / span >
b
a< span class = "synSpecial" > ))< / span >
< span class = "synSpecial" > (< / span > < span class = "synStatement" > car< / span > lis< span class = "synSpecial" > )< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > cdr< / span > lis< span class = "synSpecial" > ))))< / span >
< / pre >
< p >
これを使うと、
< / p >
< pre class = "syntax-highlight" >
gosh> < span class = "synSpecial" > (< / span > define < span class = "synSpecial" > (< / span > my_max< span class = "synStatement" > . < / span > args< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > ((< / span > pickup < span class = "synStatement" > < < / span > < span class = "synSpecial" > )< / span > args< span class = "synSpecial" > ))< / span >
my_max
gosh> < span class = "synSpecial" > (< / span > my_max < span class = "synConstant" > 1< / 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 = "synSpecial" > )< / span >
< span class = "synConstant" > 7< / span >
gosh> < span class = "synSpecial" > (< / span > define < span class = "synSpecial" > (< / span > my_min< span class = "synStatement" > . < / span > args< span class = "synSpecial" > )< / span >
< span class = "synSpecial" > ((< / span > pickup < span class = "synStatement" > > < / span > < span class = "synSpecial" > )< / span > args< span class = "synSpecial" > ))< / span >
my_min
gosh> < span class = "synSpecial" > (< / span > my_min < span class = "synConstant" > 1< / 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" > < / span > < span class = "synConstant" > 34< / span > < span class = "synSpecial" > )< / span >
< span class = "synConstant" > < / span >
< / pre >
< p >
というような書き方になります。
< / p >
< p >
感想: だいぶ理解してきた気がする。
< / p >
2019-04-02 16:06:15 +00:00
< / div >
