Functional Programming Study Plan

Functional programming study plan

This study plan was based in the LambdaConf’s Standardized Ladder of Functional Programming. It is a guide more inclined for statically-typed, category-theoretic languages, e.g. Haskell, but can be useful for all people interested in learning functional programming.

The following guide will also work as an index for future posts and/or indication of resources about those respective topics.

Enjoy!

OBS: the division in the guide using levels has the only purpose of help one to situate himself/herself in the journey of mastering FP concepts & skills.

Beginner

  • CONCEPTS
    • Immutable Data
    • Second-Order Functions
    • Constructoring & Destructuring
    • Function Composition
    • First-Class Functions & Lambdas
  • SKILLS
    • Use second-order functions (map, filter, fold) on immutable data structures
    • Destructure values to access their components
    • Use data types to represent optionality
    • Read basic type signatures
    • Pass lambdas to second-order functions

Advanced Beginner

  • CONCEPTS
    • Algebraic Data Types
    • Pattern Matching
    • Parametric Polymorphism
    • General Recursion
    • Type Classes, instances, & Laws
    • Lower-Order Abstractions (Equal, Semigroup, Monoid, etc)
    • Referential Transparency & Totality
    • Higher-Order Functions
    • Partial-Application, Currying, & Point-Free Style
  • SKILLS
    • Solve problems without nulls, exceptions, or type casts
    • Process & transform recursive data structures using recursion
    • Able to use functional programming “in the small”
    • Write basic monadic code for a concrete monad
    • Create type class instances for custom data types
    • Model a business domain with ADTs
    • Write functions that take and return functions
    • Reliably identify & isolate pure code from impure code
    • Avoid introducing unnecessary lambdas & named parameters

Intermediate

  • CONCEPTS
    • Generalized Algebraic Data Types
    • Higher-Kinded Types
    • Rank-N Types
    • Folds & Unfolds
    • Higher-Order abstractions (Category, Functor, Monad)
    • Basic Optics
    • Efficient Persistent Data Structures
    • Existential Types
    • Embedded DSLs using Combinators
  • SKILLS
    • Able to use functional programming “in the large”
    • Test code using generators and properties
    • Write imperative code in a purely functional way through monads
    • Use popular purely functional libraries to solve business problems
    • Separate decision from effects
    • Write a simple custom lawful monad
    • Write production medium-sized projects
    • Use lenses & prisms to manipulate data
    • Simplify types by hiding irrelevant data with existentials

Proficient

  • CONCEPTS
    • Codata
    • (Co)Recursion Schemes
    • Advanced Optics
    • Dual Abstractions (Comonad)
    • Monad Transformers
    • Free Monads & Extensible Effects
    • Functional Architecture
    • Advanced Functors (Exponential, Profunctors, Contravariant)
    • Embedded DSLs using GADTs, Finally Tagless
    • Advanced Monads (Continuation, Logic)
    • Type Families, Functional Dependencies
  • SKILLS
    • Design a minimally-powerful monad transformer stack
    • Write concurrent and streaming programs
    • Use purely functional mocking in tests
    • Use type classes to modularly model different effects
    • Recognize type patterns & abstract over them
    • Use functional libraries in novel ways
    • Use optics to manipulate state
    • Write custom lawful monad transformers
    • Use free monads / extensible effects to separate concerns
    • Encode invariants at the type level
    • Effectively use FDs / type families to create safer code

Expert

  • CONCEPTS
    • High-Performance
    • Kind Polymorphism
    • Generic Programming
    • Type-Level Programming
    • Dependent-Types, Singleton Types
    • Category Theory
    • Graph Reduction
    • Higher-Order Abstract Syntax
    • Compiler Design for Functional Languages
    • Profunctor Optics
  • SKILLS
    • Design a generic, lawful library with broad appeal
    • Prove properties manually using equational reasoning
    • Design & implement a new functional programming language
    • Create novel abstractions with laws
    • Write distributed systems with certain guarantees
    • Use proof systems to formally prove properties of code
    • Create libraries that do not permit invalid states
    • Use dependent-typing to prove more properties at compile-time
    • Understand deep relationships between different concepts
    • Profile, debug, & optimize purely functional code with minimal sacrifices