Retrospective

In the last (and tentatively final) step of this series we have introduced cats-effect and the IO abstraction.

Achievements

What have we achieved so far?

Features

  • creation of new row parsers from the basic string parser
  • applicative row parser combinator API
  • type class based automatic row parser derivation from case classes/constructor functions
  • domain-specific exceptions
  • row/col position reporting on parse failure

For still < 120 LoC, that doesn’t sound too bad.

Techniques

  • perusing Functor for parser derivation
  • using Applicative for parser combination
  • using type classes for automatic parser derivation
  • using Either for explicit failure mode threading
  • in general, using Functor/Applicative/Monad for chaining computations
  • using State/StateT for threading mutable state
  • using IO for side effecting code

Loose Ends

There’s still lots of things that could be done, of course.

Features

  • support more CSV features
    • headers
    • quoting/escaping
    • multiline columns
    • …
  • streaming (via fs2?)
  • other sources than files
  • …

Techniques

  • introduce more abstractions
    • Semigroup/Monoid
    • ApplicativeError/MonadError
    • Foldable
    • Traverse
    • …
  • implement Monad[Error] for RowParser
  • …

Further Reading