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by ryan davis



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oedipus_lex

a lexer generator in the same family as rexical and rex.

Oedipus Lex is a lexer generator in the same family as Rexical and Rex. Oedipus Lex is my independent lexer fork of Rexical. Rexical was in turn a fork of Rex. We’ve been unable to contact the author of rex in order to take it over, fix it up, extend it, and relicense it to MIT. So, Oedipus was written clean-room in order to bypass licensing constraints (and because bootstrapping is fun).

Oedipus brings a lot of extras to the table and at this point is only historically related to rexical. The syntax has changed enough that any rexical lexer will have to be tweaked to work inside of oedipus. At the very least, you need to add slashes to all your regexps.

Oedipus, like rexical, is based primarily on generating code much like you would a hand-written lexer. It is not a table or hash driven lexer. It use StrScanner within a multi-level case statement. As such, Oedipus matches on the first match, not the longest (like lex and its ilk).

This documentation is not meant to bypass any prerequisite knowledge on lexing or parsing. If you’d like to study the subject in further detail, please try [TIN321] or the [LLVM Tutorial] or some other good resource for CS learning. Books… books are good. I like books.

class Calculator
macros
  NUMBER /\d+/
rules
       /rpn/       :RPN # sets @state to :RPN
       /#{NUMBER}/ { [:number, text.to_i] }
       /\s+/
       /[+-]/      { [:op, text] }

  :RPN /\s+/
  :RPN /[+-]/      { [:op2, text] }
  :RPN /#{NUMBER}/ { [:number2, text.to_i] }
  :RPN /alg/       nil # clears state
end

Get The Code

If you just want to use oedipus_lex, you can install it via RubyGems:
gem install oedipus_lex
Fork me on GitHub If you want to hack on oedipus_lex, clone it from GitHub:
git clone git://github.com/seattlerb/oedipus_lex

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