F# for Fun and Profit
  • Introduction
  • Getting started
    • Contents of the book
    • "Why use F#?" in one page
    • Installing and using F#
    • F# syntax in 60 seconds
    • Learning F#
    • Troubleshooting F#
    • Low-risk ways to use F# at work
      • Twenty six low-risk ways to use F# at work
      • Using F# for development and devops scripts
      • Using F# for testing
      • Using F# for database related tasks
      • Other interesting ways of using F# at work
  • Why use F#?
    • The "Why use F#?" Series
      • Introduction to the 'Why use F#' series
      • F# syntax in 60 seconds
      • Comparing F# with C#: A simple sum
      • Comparing F# with C#: Sorting
      • Comparing F# with C#: Downloading a web page
      • Four Key Concepts
      • Conciseness
      • Type inference
      • Low overhead type definitions
      • Using functions to extract boilerplate code
      • Using functions as building blocks
      • Pattern matching for conciseness
      • Convenience
      • Out-of-the-box behavior for types
      • Functions as interfaces
      • Partial Application
      • Active patterns
      • Correctness
      • Immutability
      • Exhaustive pattern matching
      • Using the type system to ensure correct code
      • Worked example: Designing for correctness
      • Concurrency
      • Asynchronous programming
      • Messages and Agents
      • Functional Reactive Programming
      • Completeness
      • Seamless interoperation with .NET libraries
      • Anything C# can do...
      • Why use F#: Conclusion
  • Thinking Functionally
    • The "Thinking Functionally" Series
      • Thinking Functionally: Introduction
      • Mathematical functions
      • Function Values and Simple Values
      • How types work with functions
      • Currying
      • Partial application
      • Function associativity and composition
      • Defining functions
      • Function signatures
      • Organizing functions
      • Attaching functions to types
      • Worked example: A stack based calculator
  • Understanding F# ###
    • The "Expressions and syntax" Series
      • Expressions and syntax: Introduction
      • Expressions vs. statements
      • Overview of F# expressions
      • Binding with let, use, and do
      • F# syntax: indentation and verbosity
      • Parameter and value naming conventions
      • Control flow expressions
      • Exceptions
      • Match expressions
      • Formatted text using printf
      • Worked example: Parsing command line arguments
      • Worked example: Roman numerals
    • The "Understanding F# types" Series
      • Understanding F# types: Introduction
      • Overview of types in F#
      • Type abbreviations
      • Tuples
      • Records
      • Discriminated Unions
      • The Option type
      • Enum types
      • Built-in .NET types
      • Units of measure
      • Understanding type inference
    • Choosing between collection functions
    • The "Object-oriented programming in F#" Series
      • Object-oriented programming in F#: Introduction
      • Classes
      • Inheritance and abstract classes
      • Interfaces
      • Object expressions
    • The "Computation Expressions" Series
      • Computation expressions: Introduction
      • Understanding continuations
      • Introducing 'bind'
      • Computation expressions and wrapper types
      • More on wrapper types
      • Implementing a builder: Zero and Yield
      • Implementing a builder: Combine
      • Implementing a builder: Delay and Run
      • Implementing a builder: Overloading
      • Implementing a builder: Adding laziness
      • Implementing a builder: The rest of the standard methods
    • Organizing modules in a project
    • The "Dependency cycles" Series
      • Cyclic dependencies are evil
      • Refactoring to remove cyclic dependencies
      • Cycles and modularity in the wild
    • The "Porting from C#" Series
      • Porting from C# to F#: Introduction
      • Getting started with direct porting
  • Functional Design ###
    • The "Designing with types" Series
      • Designing with types: Introduction
      • Single case union types
      • Making illegal states unrepresentable
      • Discovering new concepts
      • Making state explicit
      • Constrained strings
      • Non-string types
      • Designing with types: Conclusion
    • Algebraic type sizes and domain modelling
    • Thirteen ways of looking at a turtle
      • Thirteen ways of looking at a turtle (part 2)
      • Thirteen ways of looking at a turtle - addendum
  • Functional Patterns ###
    • How to design and code a complete program
    • A functional approach to error handling (Railway oriented programming)
      • Railway oriented programming: Carbonated edition
    • The "Understanding monoids" Series
      • Monoids without tears
      • Monoids in practice
      • Working with non-monoids
    • The "Understanding Parser Combinators" Series
      • Understanding Parser Combinators
      • Building a useful set of parser combinators
      • Improving the parser library
      • Writing a JSON parser from scratch
    • The "Handling State" Series
      • Dr Frankenfunctor and the Monadster
      • Completing the body of the Monadster
      • Refactoring the Monadster
    • The "Map and Bind and Apply, Oh my!" Series
      • Understanding map and apply
      • Understanding bind
      • Using the core functions in practice
      • Understanding traverse and sequence
      • Using map, apply, bind and sequence in practice
      • Reinventing the Reader monad
      • Map and Bind and Apply, a summary
    • The "Recursive types and folds" Series
      • Introduction to recursive types
      • Catamorphism examples
      • Introducing Folds
      • Understanding Folds
      • Generic recursive types
      • Trees in the real world
    • The "A functional approach to authorization" Series
      • A functional approach to authorization
      • Constraining capabilities based on identity and role
      • Using types as access tokens
  • Testing
    • An introduction to property-based testing
    • Choosing properties for property-based testing
  • Examples and Walkthroughs
    • Worked example: Designing for correctness
    • Worked example: A stack based calculator
    • Worked example: Parsing command line arguments
    • Worked example: Roman numerals
    • Commentary on 'Roman Numerals Kata with Commentary'
    • Calculator Walkthrough: Part 1
      • Calculator Walkthrough: Part 2
      • Calculator Walkthrough: Part 3
      • Calculator Walkthrough: Part 4
    • Enterprise Tic-Tac-Toe
      • Enterprise Tic-Tac-Toe, part 2
    • Writing a JSON parser from scratch
  • Other
    • Ten reasons not to use a statically typed functional programming language
    • Why I won't be writing a monad tutorial
    • Is your programming language unreasonable?
    • We don't need no stinking UML diagrams
    • Introvert and extrovert programming languages
    • Swapping type-safety for high performance using compiler directives
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  • Should you use object-oriented features at all?
  • Understanding the object-oriented features of F# ##

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  1. Understanding F# ###
  2. The "Object-oriented programming in F#" Series

Object-oriented programming in F#: Introduction

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Last updated 5 years ago

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In this series, we'll look at how F# supports object-oriented classes and methods.

Should you use object-oriented features at all?

As has been stressed many times before, F# is fundamentally a functional language at heart, yet the OO features have been nicely integrated and do not have a "tacked-on" feeling. As a result, it is quite viable to use F# just as an OO language, as an alternative to C#, say.

Whether to use the OO style or the functional style is, of course, up to you. Here are some arguments for and against.

Reasons in favor of using OO features:

  • If you just want to do a direct port from C# without refactoring. (For more on this, there is a .)

  • If you want to use F# primarily as an OO language, as an alternative to C#.

  • If you need to integrate with other .NET languages

Reasons against using OO features:

  • If you are a beginner coming from an imperative language, classes can be a crutch that hinder your understanding of functional programming.

  • Classes do not have the convenient "out of the box" features that the "pure" F# data types have, such as built-in equality and comparison, pretty printing, etc.

  • Classes and methods do not play well with the type inference system and higher order functions (see ), so using them heavily means that you are making it harder to benefit from the most powerful parts of F#.

In most cases, the best approach is a hybrid one, primarily using pure F# types and functions to benefit from type inference, but occasionally using interfaces and classes when polymorphism is needed.

Understanding the object-oriented features of F# ##

If you do decide to use the object-oriented features of F#, the following series of posts should cover everything you need to know to be productive with classes and methods in F#.

First up, how to create classes!

entire series on how to port from C# to F#
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