2019-03-31 11:00:21 +00:00
---
title: 等価性
author: kazu634
date: 2008-08-04
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categories:
- gauche
- Lisp
---
< div class = "section" >
< p >
「二つのオブジェクトAとBが等しいとはどういうことでしょうか？
< / p >
< h4 >
内容が同じという場合
< / h4 >
< p >
二つのリストがあった場合、それぞれの要素を順に比較し、全て等しければ元のリストも等しいという立場での比較。
< / p >
< pre class = "syntax-highlight" >
gosh> < span class = "synSpecial" > (< / span > < span class = "synStatement" > equal< / span > ? < span class = "synSpecial" > (< / span > < span class = "synStatement" > list< / span > < span class = "synConstant" > 1< / span > < span class = "synConstant" > 2< / span > < span class = "synConstant" > 3< / span > < span class = "synSpecial" > )< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > list< / span > < span class = "synConstant" > 1< / span > < span class = "synConstant" > 2< / span > < span class = "synConstant" > 3< / span > < span class = "synSpecial" > ))< / span >
#<span class="synStatement">t</span>
gosh> < span class = "synSpecial" > (< / span > < span class = "synStatement" > equal< / span > ? < span class = "synSpecial" > (< / span > < span class = "synStatement" > list< / span > < span class = "synConstant" > 1< / span > < span class = "synConstant" > 2< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > list< / span > < span class = "synConstant" > 3< / span > < span class = "synConstant" > 4< / span > < span class = "synSpecial" > )< / span > < span class = "synConstant" > 5< / span > < span class = "synSpecial" > )< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > cons< / span > < span class = "synConstant" > 1< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > cons< / span > < span class = "synConstant" > 2< / span > < span class = "synSpecial" > '((< / span > 3 4< span class = "synSpecial" > )< / span > . < span class = "synSpecial" > (< / span > 5< span class = "synSpecial" > )))))< / span >
#<span class="synStatement">t</span>
gosh> < span class = "synSpecial" > (< / span > < span class = "synStatement" > equal< / span > ? < span class = "synSpecial" > (< / span > < span class = "synStatement" > list< / span > < span class = "synConstant" > 1< / span > < span class = "synConstant" > 2< / span > < span class = "synConstant" > 3< / span > < span class = "synSpecial" > )< / span > < span class = "synSpecial" > (< / span > < span class = "synStatement" > list< / span > < span class = "synConstant" > 1< / span > < span class = "synConstant" > 2< / span > < span class = "synConstant" > 4< / span > < span class = "synSpecial" > ))< / span >
#f
< / pre >
< h4 >
入れ物が同じ
< / h4 >
< p >
他の値を入れておく入れ物の同一性を調べるもの。C言語を知っている人は、eq?はオブジェクトの「アドレス」を比較していると考えていい。
< / p >
< pre class = "syntax-highlight" >
gosh> < span class = "synSpecial" > (< / span > < span class = "synStatement" > eq< / span > ? < 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 = "synStatement" > cons< / span > < span class = "synConstant" > 1< / span > < span class = "synConstant" > 2< / span > < span class = "synSpecial" > ))< / span >
#f
gosh> < span class = "synSpecial" > (< / span > define p < span class = "synSpecial" > (< / span > < span class = "synStatement" > cons< / span > < span class = "synConstant" > 1< / span > < span class = "synConstant" > 2< / span > < span class = "synSpecial" > ))< / span >
p
gosh> < span class = "synSpecial" > (< / span > < span class = "synStatement" > eq< / span > ? p p< span class = "synSpecial" > )< / span >
#<span class="synStatement">t</span>
< / pre >
< h4 >
数値として同じ
< / h4 >
< p >
数値として比較する場合。
< / p >
< pre class = "syntax-highlight" >
gosh> < span class = "synSpecial" > (< / span > eqv? < span class = "synConstant" > 1< / span > < span class = "synConstant" > 1< / span > < span class = "synSpecial" > )< / span >
#<span class="synStatement">t</span>
gosh> < span class = "synSpecial" > (< / span > eqv? < span class = "synConstant" > 1.0< / span > < span class = "synConstant" > 1.0< / span > < span class = "synSpecial" > )< / span >
#<span class="synStatement">t</span>
gosh> < span class = "synSpecial" > (< / span > eqv? < span class = "synConstant" > 1< / span > < span class = "synConstant" > 1.0< / span > < span class = "synSpecial" > )< / span >
#f
gosh> < span class = "synSpecial" > (< / span > < span class = "synStatement" > =< / span > < span class = "synConstant" > 1< / span > < span class = "synConstant" > 1.0< / span > < span class = "synSpecial" > )< / span >
#<span class="synStatement">t</span>
gosh> < span class = "synSpecial" > (</ span >< span class = "synStatement" > char=</ span > ? #\a #\a< span class = "synSpecial" > )</ span >
#<span class="synStatement">t</span>
gosh> < span class = "synSpecial" > (</ span >< span class = "synStatement" > char=</ span > ? #\a < span class = "synType" > #\A</ span >< span class = "synSpecial" > )</ span >
#f
gosh> < span class = "synSpecial" > (< / span > < span class = "synStatement" > string=< / span > ? < span class = "synConstant" > " abc" < / span > < span class = "synConstant" > " abc" < / span > < span class = "synSpecial" > )< / span >
#<span class="synStatement">t</span>
gosh> < span class = "synSpecial" > (< / span > < span class = "synStatement" > string=< / span > ? < span class = "synConstant" > " abc" < / span > < span class = "synConstant" > " ABC" < / span > < span class = "synSpecial" > )< / span >
#f
< / pre >
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