A common hurdle in the journey to serious FP use is being able to make the jump from functional programming in the small to being able to write non-trivial applications that are easily configurable and clearly delineate side effects and error conditions.

In this talk, we will introduce ExceptT and run through what you need to know to consume a monad transformer as a user. We'll then combine this with ReaderT for configuration and then look into the lovely MonadReader, MonadError and MonadIO typeclasses and how they make things even nicer.

At the very least, with this knowledge you should start having a much easier time consuming effectful haskell APIs (e.g. Persistent, Snap) as they are heavily based around these ideas. At best, you'll be equipped to start writing non-trivial FP programs for fun and profit.

The talk will be accompanied with a full-working program that you'll be able to tinker with and learn from outside of the talk; written in much the same style as the production haskell code written at iseek.