Homework code for the "Hoodlums" London Haskell Meetup group

201010_Parser:

• Task: Implement a parser for a simple expression tree.
• Contents:
  • Expressions.hs: The expression tree implementation, some demonstration catamorphisms.
  • MonadicParser.hs: A parser combinator library implementation, using a monadic style.
    Based on code from the October Hoodlums meeting and from the 1998 paper "Monadic parsing in Haskell" by Hutton and Meijer. Running a parser returns a list of possible results; an empty list indicates an error.
  • ApplicativeParser.hs: A parser combinator library implementation, using an applicative style. NB: uses a different parser model than MonadicParser.hs --- returns an "Either", with left indicating an error (Left (err, remaining string)), right indicating a successful parse (Right (result, remaining string)).
  • MonadicExpressionParser.hs, ApplicativeExpressionParser.hs: Parsers for the expression language in "Expressions.hs", using the Monadic or Applicative style.
  • main.hs: A simple program to test the above; takes a string from the user and attempts to parse using the monadic and applicative parsers, doing some simple error checking.
    • compile with ghc --make main