Three levels of understanding

Conceptual Theoretical Craft

Conceptual level

Properties of good code:

• Readable
• Scalable
• Modular
• Maintainable / Testable
• Composable / Closure
• Predictable / Statically typed

Big theory patterns

1. ADTs
   • Sum types -- sealed traits
   • Product types -- case classes
2. Sequencing methods:
   • map
   • flatMap
   • foldLeft/Right
3. Type classes
   • A definition of some functionality that we want to implement for a wide range of data types

Introductions

• Name
• How much Scala
• How much Cats
• What do you want to get out of the course

Parts of this course

• Toolbox
  • Type classes
    • Semigroup and Monoid
    • Functor, Monad, and MonadError
    • Semigroupal, Applicative
    • Parallel
    • Foldable and Traverse
  • Data types
    • Option, Either, Future, Try
    • Monad transformers
    • Eval
    • Validated
    • (maybe Reader, Writer, and State)
• Intepreter pattern
  • Tagless final encoding
  • aka Finally tagless encoding
  • (maybe natural transformations)
• Workshop

Setup

open https://underscore.io/books/scala-with-cats

sbt new underscoreio/cats-seed.g8
# We're using:
# - Scala 2.12
# - Cats 1.4
# - Kind projector

git clone https://github.com/typelevel/cats.git

(We'll be looking at the code to find out how things work!)

Type classes