Scala with Cats

Modules

Chapter Checklist

• 1 Introduction
  • 1.1 Anatomy of a Type Class
  • 1.1.1 The Type Class
  • 1.1.2 Type Class Instances
  • 1.1.3 Type Class Use
  • 1.2 Working with Implicits
  • 1.2.1 Packaging Implicits
  • 1.2.2 Implicit Scope
  • 1.2.3 Recursive Implicit Resolution
  • 1.3 Exercise: Printable Library
  • 1.4 Meet Cats
  • 1.4.1 Importing Type Classes
  • 1.4.2 Importing Default Instances
  • 1.4.3 Importing Interface Syntax
  • 1.4.4 Importing All The Things!
  • 1.4.5 Defining Custom Instances
  • 1.4.6 Exercise: Cat Show
  • 1.5 Example: Eq
  • 1.5.1 Equality, Liberty, and Fraternity
  • 1.5.2 Comparing Ints
  • 1.5.3 Comparing Options
  • 1.5.4 Comparing Custom Types
  • 1.5.5 Exercise: Equality, Liberty, and Felinity
  • 1.6 Controlling Instance Selection
  • 1.6.1 Variance
  • 1.7 Summary
• 2 Monoids and Semigroups
  • 2.1 Definition of a Monoid
  • 2.2 Definition of a Semigroup
  • 2.3 Exercise: The Truth About Monoids
  • 2.4 Exercise: All Set for Monoids
  • 2.5 Monoids in Cats
  • 2.5.1 The Monoid Type Class
  • 2.5.2 Monoid Instances
  • 2.5.3 Monoid Syntax
  • 2.5.4 Exercise: Adding All The Things
  • 2.6 Applications of Monoids
  • 2.6.1 Big Data
  • 2.6.2 Distributed Systems
  • 2.6.3 Monoids in the Small
  • 2.7 Summary
• 3 Functors
  • 3.1 Examples of Functors
  • 3.2 More Examples of Functors
  • 3.3 Definition of a Functor
  • 3.4 Aside: Higher Kinds and Type Constructors
  • 3.5 Functors in Cats
  • 3.5.1 The Functor Type Class and Instances
  • 3.5.2 Functor Syntax
  • 3.5.3 Instances for Custom Types
  • 3.5.4 Exercise: Branching out with Functors
  • 3.5.5 Contravariant Functors and the contramap Method
  • 3.5.6 Invariant functors and the imap method
  • 3.6 Contravariant and Invariant in Cats
  • 3.6.1 Contravariant in Cats
  • 3.6.2 Invariant in Cats
  • 3.7 Aside: Partial Unification
  • 3.7.1 Limitations of Partial Unification
  • 3.8 Summary
• 4 Monads
  • 4.1 What is a Monad?
  • 4.1.1 Definition of a Monad
  • 4.1.2 Exercise: Getting Func-y
  • 4.2 Monads in Cats
  • 4.2.1 The Monad Type Class
  • 4.2.2 Default Instances
  • 4.2.3 Monad Syntax
  • 4.3 The Identity Monad
  • 4.3.1 Exercise: Monadic Secret Identities
  • 4.4 Either
  • 4.4.1 Left and Right Bias
  • 4.4.2 Creating Instances
  • 4.4.3 Transforming Eithers
  • 4.4.4 Error Handling
  • 4.4.5 Exercise: What is Best?
  • 4.5 Aside: Error Handling and MonadError
  • 4.5.1 The MonadError Type Class
  • 4.5.2 Raising and Handling Errors
  • 4.5.3 Instances of MonadError
  • 4.5.4 Exercise: Abstracting
  • 4.6 The Eval Monad
  • 4.6.1 Eager, Lazy, Memoized, Oh My!
  • 4.6.2 Eval’s Models of Evaluation
  • 4.6.3 Eval as a Monad
  • 4.6.4 Trampolining and Eval.defer
  • 4.6.5 Exercise: Safer Folding using Eval
  • 4.7 The Writer Monad
  • 4.7.1 Creating and Unpacking Writers
  • 4.7.2 Composing and Transforming Writers
  • 4.7.3 Exercise: Show Your Working
  • 4.8 The Reader Monad
  • 4.8.1 Creating and Unpacking Readers
  • 4.8.2 Composing Readers
  • 4.8.3 Exercise: Hacking on Readers
  • 4.8.4 When to Use Readers?
  • 4.9 The State Monad
  • 4.9.1 Creating and Unpacking State
  • 4.9.2 Composing and Transforming State
  • 4.9.3 Exercise: Post-Order Calculator
  • 4.10 Defining Custom Monads
  • 4.10.1 Exercise: Branching out Further with Monads
  • 4.11 Summary
• 5 Monad Transformers
  • 5.1 Exercise: Composing Monads
  • 5.2 A Transformative Example
  • 5.3 Monad Transformers in Cats
  • 5.3.1 The Monad Transformer Classes
  • 5.3.2 Building Monad Stacks
  • 5.3.3 Constructing and Unpacking Instances
  • 5.3.4 Default Instances
  • 5.3.5 Usage Patterns
  • 5.4 Exercise: Monads: Transform and Roll Out
  • 5.5 Summary
• 6 Semigroupal and Applicative
  • 6.1 Semigroupal
  • 6.1.1 Joining Two Contexts
  • 6.1.2 Joining Three or More Contexts
  • 6.1.3 Semigroupal Laws
  • 6.2 Apply Syntax
  • 6.2.1 Fancy Functors and Apply Syntax
  • 6.3 Semigroupal Applied to Different Types
  • 6.3.1 Semigroupal Applied to Monads
  • 6.4 Parallel
  • 6.5 Apply and Applicative
  • 6.5.1 The Hierarchy of Sequencing Type Classes
  • 6.6 Summary
• 7 Foldable and Traverse
  • 7.1 Foldable
  • 7.1.1 Folds and Folding
  • 7.1.2 Exercise: Reflecting on Folds
  • 7.1.3 Exercise: Scaf-fold-ing Other Methods
  • 7.1.4 Foldable in Cats
  • 7.2 Traverse
  • 7.2.1 Traversing with Futures
  • 7.2.2 Traversing with Applicatives
  • 7.2.3 Traverse in Cats
  • 7.3 Summary
• 8 Case Study: Testing Asynchronous Code
  • 8.1 Abstracting over Type Constructors
  • 8.2 Abstracting over Monads
  • 8.3 Summary
• 9 Case Study: Map-Reduce
  • 9.1 Parallelizing map and fold
  • 9.2 Implementing foldMap
  • 9.3 Parallelising foldMap
  • 9.3.1 Futures, Thread Pools, and ExecutionContexts
  • 9.3.2 Dividing Work
  • 9.3.3 Implementing parallelFoldMap
  • 9.3.4 parallelFoldMap with more Cats
  • 9.4 Summary
• 10 Case Study: Data Validation
  • 10.1 Sketching the Library Structure
  • 10.2 The Check Datatype
  • 10.3 Basic Combinators
  • 10.4 Transforming Data
  • 10.4.1 Predicates
  • 10.4.2 Checks
  • 10.4.3 Recap
  • 10.5 Kleislis
  • 10.6 Summary
• 11 Case Study: CRDTs
  • 11.1 Eventual Consistency
  • 11.2 The GCounter
  • 11.2.1 Simple Counters
  • 11.2.2 GCounters
  • 11.2.3 Exercise: GCounter Implementation
  • 11.3 Generalisation
  • 11.3.1 Implementation
  • 11.3.2 Exercise: BoundedSemiLattice Instances
  • 11.3.3 Exercise: Generic GCounter
  • 11.4 Abstracting GCounter to a Type Class
  • 11.5 Abstracting a Key Value Store
  • 11.6 Summary