Funcprog 2022 recap

• GraphQL API tests with Snowflaqe
• Functors and Monads as an abstraction

  • ​List<T>

  • Option<T> (Nullable<T>)

  • Result<T, E>

• Computation expressions
  • async/await
  • error handling
  • any other monad

Main "Principles" of Functional Programming

Immutability

Pure functions

C#

• Immutable data structures
  • Records (without public setters!)
  • Readonly/Immutable collections
  • LINQ
• Pure functions
  • [Pure] attribute
  • static methods (prevents accessing "this")

Differences between FP and OOP

OOP

Data and operations over data tied together (classes)

FP

Data structures decoupled from operations over data (functions)

Goals of a functional approach

• Easier to reason about code due to
  • data modelling (type driven approach)
  • immutability (no need to track changes)
  • smaller chunks of code (functions)
  • reliance on (trustworthy) type signatures
  • explicitness (argument passing, no implicit "this")
  • etc
• Prevent bugs/race conditions due to mutating shared state
• Compile-time safety
• Unit testing without mocks (pure functions)

C#: The final missing piece

State of Discriminated Union