Arithmetic expression parser using Parsec (2)

Previous post: Arithmetic expression parser using Parsec

Sorry, I am too lazy to explain them step by step again,
so I no longer write this in literate haskell.
Please read the source on github directly.

* calculator.lhs (previous one)
* calculator-lex.hs (adding lexer)
* calculator-ast.hs (adding ast)

A source to source translator walking through the AST:

* Translator.hs
* Ast.hs
* Test.hs

Next step: Try to parse class definition for an object-oriented language