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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166
6
章 無からのプログラミング
その単純さにも関わらず、これを機能の足りないプログラミング言語で作ろうとすると、非常に野心
的なプログラムになります。このプログラムにはかなりの組み込みのRuby 機能が使われています。
Range
オブジェクトを生成し、それを
map
メソッドで使い、巨大な条件文を評価し、剰余演算子で計
算をし、
Fixnum#zero?
述語メソッドを使い、文字列リテラルを使い、
Fixnum#to_s
で数を文字列
に変換しています。私たちはこれらをすべて引き剥がして、procを使って再実装していく必要があり
ます。
6.1.3
数
まずは、FizzBuzzに登場する数に注目しましょう。どうすれば
Fixnum
などのRuby が提供する
データ型を使わずに、数を表現できるのでしょうか。
ゼロから数を実装しようとするなら
†
、まず実装しようとするものをきちんと理解しなくてはなりませ
ん。数とは一体何なのでしょうか。定義しようとしているものの別の側面をうっかり前提にしないよ
う、具体的な定義を考え出すのは難しいことです。たとえば「いくつであるか教えてくれるもの」とい
う定義は役に立ちません。なぜなら「いくつか」というのは、実のところ「数」の別の言い方にすぎな
いためです。
数を特徴付ける方法が1つあります。リンゴの入った袋とオレンジの入った袋があるとしましょう。
リンゴの袋からリンゴを1つ、オレンジの袋からオレンジを1 つ取り出します。そして、少なくともど
ちらかの袋が空になるまで、リンゴとオレンジを取
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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.