ruby-dev

稲葉です.

Subject: [ruby-dev:7005] Re: ruby lacks some features of tr in Perl
From: matz@netlab.co.jp (Yukihiro Matsumoto)
Date: Thu, 27 May 1999 17:57:56 +0900

> まつもと ゆきひろです
> 
> In message "[ruby-dev:6992] ruby lacks some features of tr in Perl"
>     on 99/05/25, Inaba Hiroto <inaba@st.rim.or.jp> writes:
> 
> |tr///dはString#delete、tr///sはString#tr_sとメソッドを用意しているのだ
> |から、String#countというある範囲の文字の数を数えるメソッドがあってもい
> |いと思いますが、どうでしょうか？
> 
> 良さそうに思います．わたなべさんからは histgram は？ という
> 意見も出てるようですが，どのような仕様のメソッドが良いでしょ
> うねえ．

個人的には, 単に範囲に含まれる文字数を返すだけでいいと思います.

文字数0の時nilにする事も考えられますが, nonzero?があるのでそうしなくて
いいでしょう.

# Perl5 の Todo に「リストコンテキストのtr///で histgramを返す？」とい
# うのが(まだ)ありますね. これが無意識にあって「スカラーコンテキストで」
# なんて書いてしまったのかな.

> # 1.3はfreezeしてるので1.4以降ですね．

OKです.

> |２．rubyのString#deleteはPerlのtr///dでできる「ある範囲に含まれある
> |範囲に含まれない」文字の削除ができません。
> |  % perl -le '$_ = "123456789"; tr/2-8/4-6/d; print'
> |  14569
> 
> deleteがoptionalな2番目の引数を持てば良いようですね．そうし
> ようかな．

Perlのtr///dの移植にはそれで十分ですが, 任意個の引数を持てるようにして
対象範囲はそれらのANDとするのはどうでしょう. 上で提案したString#count
もそうできますね.

  ruby -e 'p "123456789".delete("2-8", "^4-6")' # => "14569"

2引数までに限るとしても, ANDの方がわかりやすいと思います.
--
	稲葉 浩人 <inaba@sdd.tokyo-sc.toshiba.co.jp/inaba@st.rim.or.jp>

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[ruby-dev:7010] Re: ruby lacks some features of tr in Perl

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[#6783] Re: Ruby 1.3.3-990507 — 助田　雅紀 <masaki.suketa@...>

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