From: MAEDA Shugo <shugo@...>
Date: 1998-06-23T23:09:03+09:00
Subject: [ruby-list:8486] cursor

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前田です。

以前少し話題にのぼった外部イテレータのライブラリを作ってみました。

使い方は、

require "cursor"

ary = [1, 2, 3]
i = ary.cursor
until i.done?
  p i.current
  i.next
end

といった感じです。

def pareach(*args)
  cursors = args.collect { |i| i.cursor }
  until cursors.find { |c| c.done? }
    yield(*cursors.collect { |c| c.current })
    cursors.each { |c| c.next }
  end
end

ary1 = [1, 2, 3]
ary2 = ["one", "two", "three"]

pareach(ary1, ary2) { |i1, i2|
  print i1, ":", i2, "＼n"
}

などとすると並行eachが書けます。
# 並行eachといってもマルチスレッドではないです(^^;

Cで書いたのはスピードのためです。
でもやっぱり内部イテレータの方が楽だし速いですね。

ところで、until condよりwhile !condの方が速いのですね。
ちょっと意外でした。
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前田 修吾
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