Contents

1. day 0
   • Intro to Cats
   1. What is polymorphism?
      • Parametric polymorphism
      • Subtype polymorphism
      • Ad-hoc polymorphism
   2. sum function
      • Monoid
   3. FoldLeft
      • Typeclasses in Cats
   4. Method injection (enrich my library)
      • Operator syntax for the standard datatypes
2. day 1
   • typeclasses 101
   1. sbt
   2. Eq
   3. Order
   4. PartialOrder
   5. Show
   6. Read
   7. Enum
   8. Numeric
   9. typeclasses 102
      • A traffic light datatype
3. day 2
   1. Making our own typeclass with simulacrum
      • Yes-No typeclass
   2. Functor
      • Either as a functor
      • Function as a functor
      • Lifting a function
   3. Checking laws with Discipline
      • Checking laws from the REPL
      • Checking laws with Discipline + MUnit
      • Breaking the law
   4. Import guide
      • Implicits review
      • import cats._
      • Implicit scope
      • import cats.data._
      • import cats.implicits._
        • cats.instances.AllInstances
        • cats.syntax.AllSyntax
      • a la carte style
        • typeclass instances
        • Cats typeclass syntax
        • Cats datatype syntax
        • standard datatype syntax
        • all syntax
4. day 3
   1. Kinds and some type-foo
      • forms-a vs is-a
   2. Semigroupal
      • Cartesian law
   3. Apply
      • The Applicative Style
      • List as a Apply
      • *> and <* operators
      • Option syntax
      • Option as an Apply
      • Useful functions for Apply
      • Apply law
   4. Applicative
      • Useful functions for Applicative
      • Applicative Laws
5. day 4
   1. Semigroup
      • The Semigroup typeclass
      • The Semigroup Laws
      • Lists are Semigroups
      • Product and Sum
   2. Monoid
      • Monoid typeclass
      • Monoid laws
      • Value classes
      • Disjunction and Conjunction
      • Option as Monoids
   3. About Laws
   4. Using monoids to fold data structures
6. day 5
   • Apply.ap
   • Serializable typeclass instance
   1. FlatMap
      • Getting our feet wet with Option
      • FlatMap laws
   2. Monad
      • Walk the line
      • Banana on wire
      • for comprehension
      • Pierre returns
      • Pattern matching and failure
      • Monad laws
   3. List datatype
   4. FunctorFilter
   5. A knight’s quest
7. day 6
   1. do vs for
      • Implementing actM
   2. Writer datatype
      • Writer
      • WriterT
      • Using for syntax with Writer
      • Adding logging to program
      • Inefficient List construction
      • Comparing performance
   3. Reader datatype
      • Dependency injection
8. day 7
   1. State datatype
      • State and StateT datatype
      • Getting and setting the state
      • Extracting and modifying the state
   2. Validated datatype
      • Using NonEmptyList to accumulate failures
   3. Ior datatype
9. day 8
   1. Free monoids
      • Injective
      • Uniqueness
      • Free objects
   2. Free monads
      • Why free monads matter
      • CharToy
      • Fix
      • FixE
      • Free datatype
   3. Stackless Scala with Free Monads
      • Trampoline
      • Free monads
      • Free monoid using Free
   4. Tail Recursive Monads (FlatMap)
      • The stack problem
      • FlatMap (MonadRec)
10. day 9
    1. Some useful monadic functions
       • flatten method
       • filterM method
       • foldM function
    2. Making a safe RPN calculator
    3. Composing monadic functions
       • lift method
    4. Making monads
    5. Monads are fractals
       • List forms a monad under ++
       • Option forms a monad under?
       • State as a fractal
       • Look out for fractals
11. day 10
    1. Monad transformers
       • Dependency injection again
       • Kleisli as ReaderT
    2. Stacking Future and Either
       • EitherT datatype
12. day 11
    1. Genericity
       • Genericity by value
       • Genericity by type
       • Genericity by function
       • Genericity by structure
       • Genericity by property
       • Genericity by stage
       • Genericity by shape
    2. Datatype-generic programming with Bifunctor
       • Bifunctor
       • Deriving map from Bifunctor
       • Deriving fold from Bifunctor
       • Deriving unfold from Bifunctor
       • Tree
       • The Origami patterns
    3. Const datatype
       • Monoidal applicative functors using Const datatype
    4. Combining applicative functors
       • Product of functors
       • Product of apply functors
       • Product of applicative functors
       • Composition of Applicative
       • Product of applicative functions
       • Composition of applicative functions
13. day 12
    1. Traverse
       • sequence function
    2. TraverseFilter
       • filterA
    3. Coercing type inference using partial unification
    4. Shape and contents
    5. Applicative wordcount
       • Modular iterations, applicatively
14. day 13
    1. Id datatype
       • Id as Functor
       • Id as Apply
       • Id as FlatMap
       • What s the point of Id?
    2. Eval datatype
       • Eval.later
       • Eval.now
       • Eval.always
       • stack-safe lazy computation
    3. The Abstract Future
       • UserRepos with Future
       • UserRepos with Id
       • Coding in abstract
       • UserRepos with EitherT
15. day 14
    1. SemigroupK
       • Option as SemigroupK
       • SemigroupK laws
    2. MonoidK
       • MonoidK laws
    3. Alternative
       • Alternative laws
       • Wolf, Goat, Cabbage
       • makeNMoves0
       • isSolution
       • makeMove
16. day 15
    1. Basic category theory
       • Sets, arrows, composition
       • Point
    2. Arrow
       • Category
       • Compose
       • Strong
       • Split
    3. Isomorphism
       • Equality of arrows
       • Testing for isomorphism
17. day 16
    • Awodey s Category Theory
    • Milewski s Category Theory for Programmers
    1. Sets
       • Sets
    2. Pos
    3. Finite categories
    4. Cat
    5. Monoid as categories
       • Mon
    6. Grp
       • Forgetful functor
18. day 17
    1. Initial and terminal objects
       • Uniquely determined up to isomorphism
       • Examples of initial objects
       • Examples of terminal objects
    2. Product
       • Uniqueness of products
    3. Duality
       • Opposite category
       • The duality principle
    4. Coproduct
       • Algebraic datatype
       • Either datatype as coproduct
       • Curry-Howard encoding
       • Shapeless.Coproduct
       • EitherK datatype
19. day 18
    1. Effect system
       • Cats Effect sbt setup
    2. IO datatype
       • Hello world
       • Pizza app
    3. ApplicativeError
       • Either as ApplicativeError
       • scala.util.Try as ApplicativeError
       • IO as ApplicativeError
    4. MonadCancel
       • IO as MonadCancel
       • F.uncancelable
       • bracket
20. day 19
    1. FunctionK
       • Higher-Rank Polymorphism in Scala
       • FunctionK in MonadCancel
    2. Resource datatype
       • Resource as Monad
       • Resource cancellation
    3. Ref as monad transformer
       • Resource as monad transformer
21. Contents in Depth
22. Combined Pages