This is the demo code for a talk about Iteratees held at the Regensburg Haskell Meetup at December 3rd, 2014. It consists of implementations of Iteratees both pure and as monad transformers, along with a small set of examples that demonstrate various features.

You might want to start with looking at the examples in LazyIO which demonstrate two well-known problems with lazy IO in Haskell. After that have a look at the implementation of pure Iteratees in RHM.Intern.Pure as well as the corresponding examples to be found in the RHM.Iteratee and the Main module.

Note that the pure implementation is largely (if not at all) redundant when the transformer variant is used instead (see e.g. StateT and State).

Install the project's dependencies into a cabal sandbox:

cabal sandbox init
cabal install --only-dependencies
cabal build

Quickly browse through the examples in src/LazyIO.hs and run the demo with

cabal run lazyio-demo FILENAME

Replace FILENAME with an existing file (will be opened read-only). Adapt the code to run other examples.

Run the iteratee demo with

cabal run iter-demo

Either adapt the code or (preferably) start a REPL session with cabal repl.

• John W. Lato: "Iteratee: Teaching an Old Fold New Tricks", Monad Reader #16
  http://themonadreader.files.wordpress.com/2010/05/issue16.pdf

• Oleg Kiselyov:

  • Web root:
    http://okmij.org/ftp/Streams.html

  • "Iteratees"
    http://okmij.org/ftp/Haskell/Iteratee/describe.pdf

  • Annotated slides corresponding to the talk at FLOPS 2012
    http://okmij.org/ftp/Haskell/Iteratee/talk-FLOPS.pdf

  • "Lazy IO breaks equational reasoning"
    http://okmij.org/ftp/Haskell/index.html#lazyIO-not-True

• Edward Kmett: "A Parsing Trifecta", Boston Area Haskell User Group 2009
  http://comonad.com/reader/2009/iteratees-parsec-and-monoid/