September 2014
Intermediate to advanced
336 pages
7h 53m
Japanese
Content preview from アンダースタンディング コンピュテーション ―単純な機械から不可能なプログラムまで
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292
9
章 おもちゃの国のプログラミング
ジェクト（
Fixnum
）か抽象的なオブジェクト（
Sign
）かによらず、まったく同じRuby式で具体的な
計算と抽 象的な計 算 が実 行できることに注意しましょう。3つの 数をある方 法で 掛け 算する
#calculate
メソッドについて見てみましょう。
def calculate(x, y, z)
(x
*
y)
*
(x
*
z)
end
Fixnum
オブジェクトを引数として
#calculate
を呼び出すと、計算は
Fixnum#
*
によって行わ
れ、具体的な
Fixnum
の結果が得られます。代わりに
Sign
インスタンスで呼び出すと、
Sign#
*
の演
算が実行され、抽象的な
Sign
の結果が得られます。
>>
calculate(3, -5, 0)
=> 0
>>
calculate(Sign::POSITIVE, Sign::NEGATIVE, Sign::ZERO)
=> #<Sign zero>
このように他のコードを変更することなく、具体的な引数を抽象的な引数に変えて実行することに
よって、限定的ながら、実際のRubyプログラムで抽象解釈を行うことができます。
このテクニックは、自動ユニットテストで使われるテストダブル（たとえば、スタブやモック）
を思い出させます。テストダブルとは、プログラムの振る舞いを制御、変更するためにコード
に注入される、特殊なプレースホルダオブジェクトのことです。より現実的なオブジェクトを
テストデータとして使うと不都合があったりコストがか ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.