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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126
4
章 能力を高める
字句解析（Lexical analysis）
生の文字列を読んで、トークン（token）のシーケンスに変換します。それぞれのトークンは「変
数名」、「開き括弧」、「
while
キーワード」といった、プログラム構文の個々の構成要素を表現しま
す。字句解析器は字句文法（lexical grammar）と呼ばれる言語固有の規則の集合を使って、文字
のシーケンスがどのトークンを生成するかを決めます。このステージでは、変数の命名規則、コ
メント、空白といった厄介な文字レベルの詳細に取り組み、次のステージで使う、きれいなトーク
ンのシーケンスを残します。
構文解析（Syntactic analysis）
トークンのシーケンスを読んで、パースされる言語の構文文法（syntactic grammar）にしたがっ
て、有効なプログラムを表現しているか判断します。もし有効なプログラムであれば、構文解析
器は構造に関する追加の情報（たとえば、構文木）を生成します。
4.3.1
字句解析
字句解析ステージは通常、非常にわかりやすいものです。これは正規表現を使って（すなわち、
NFAによって）実現することができます。なぜなら、ここで必要なのは、単なる文字のフラットなシー
ケンスをいくつかの規則にマッチさせ、それらをキーワード、変数名、演算子などに判別することだけ
だからです。SIMPLEプログラムをトークンに切り分けるための、とりあえずのRubyコードは以下の
ようになります。
class LexicalAnalyzer ...
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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.