字句解析Lexing

• 字句解析の大半は単純なパターンマッチの問題

  Lexing is mostly a matter of simple pattern matching

• Perlにはまさにうってつけの正規表現がある

  Perl actually has special regex features just for this purpose

• 時間の都合でほとんど説明できないけれど

  Most of which alas, I have no time to explain

• 『Higher-Order Perl』に書いておいたので読んでね

  It is in the book, though

• 『詳説 正規表現』にも書いてあるよ

  Also in Friedl's book

• こんな感じの@tokensがあるとしよう

  We will assume that @tokens looks something like this:

        # (x^2 + 3*x) * sin(x * 2) + 14
        (["("], ["VAR", "x"], ["^"], ["NUMBER", 2], ["+"],
         ["NUMBER", 3], ["*"],  ["VAR", "x"], [")"],
         ["FUNCTION", "sin"], ["("], ["VAR", "x"], ["*"],
         ["NUMBER", 2], [")"], ["+"], ["NUMBER", 14])

• それから

  Also:

        sub type  { my $token = shift; $token->[0] }
        sub value { my $token = shift; $token->[1] }

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Copyright © 2007 M. J. Dominus