Madrid F# Meetup: Introduction to F#
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This document summarizes an introduction to F# presentation given at a Madrid F# meetup. The presenter introduces themselves and explains that the talk will provide an overview of F# based on their personal experience, and will focus more on practical than theoretical aspects. They then discuss what F# is, its type system including tuples, records, discriminated unions and built-in types, as well as features like pattern matching, units of measure, and type providers. Real-world applications and platforms that F# supports are also mentioned.
Madrid F# Meetup: Introduction to F#
- 1. MADRID F# MEETUP Introduction to F#
- 2. MADRID F# MEETUP About me Alfonso García-Caro Independent Developer Studied IT but got degree in Linguistics Japanese speaker .NET fanboy Started F# recently More pragmatic than theoretical @alfonsogcnunez github.com/alfonsogarciacaro
- 3. MADRID F# MEETUP About this talk Not official nor comprehensive Mostly based in personal experience Not an introduction to functional programming Please ask if you need more detail Will “borrow” from other F#ers Particularly @ScottWlaschin fsharp.org fsharpforfunandprofit.com
- 4. MADRID F# MEETUP What is F#? F# is an open source, cross-platform, strongly-typed, functional-first programming language. It offers interoperability with all .NET languages and libraries and data-rich analytical services like type providers and LINQ queries.
- 5. FunScript F# to JavaScript with type providers MADRID F# MEETUP
- 6. MADRID F# MEETUP F# is... robust Its powerful type system prevents many common errors (null references) and allows you to encode business logic to make illegal states unrepresentable. Yaron minsky via fsharpforfunandprofit.com
- 7. MADRID F# MEETUP Model Problem: A contact must have an email or a postal address Naïve solution Solution with union types
- 8. MADRID F# MEETUP F# types: Tuples • No explicit names • Can have any number of components • Components can be generic o complex types • Most often used to return multiple values from private functions
- 9. MADRID F# MEETUP F# types: Records • Like tuples with labels • Structural equality by default • Can have members
- 10. MADRID F# MEETUP F# types: Discriminated Unions • Mostly used with pattern matching • Can be recursive • Can have field names (tuple labels) • Empty cases possible • Option union instead of null
- 11. MADRID F# MEETUP F# types: Discriminated Unions Construction Pattern matching: Check case and deconstruct all-in-one
- 12. MADRID F# MEETUP F# types: unit • No void functions • Single value: () • Automatically ignored F# types: Abbreviations Use an alias for convenience (no type-safe) These ones are built-in
- 13. MADRID F# MEETUP F# types: Collections Many built-in functions to deal with sequences: map, reduce, fold, find... • Immutable oRecursive lists oSet and maps oLazy sequences • Mutable oArray oBuilt-in .NET collections: Lists, Dictionaries... • Also ranges and comprehensions All collections are generic
- 14. MADRID F# MEETUP F# types: Built-in .NET Types • Built-in value types: int, bool... • Built-in reference types: string... • User-defined value types: enum and struct • Classes and interfaces • Delegates Not the same as F# functions but they can be converted Also pointers, but they are not usually needed
- 15. FunScript F# to JavaScript with type providers MADRID F# MEETUP YOU SAY STATIC TYPING I HEAR BOILERPLATE
- 16. MADRID F# MEETUP F# is... agile Type inference reduces the number of type annotations, bringing together the benefits of static typing and the conciseness of dynamic typing. C# F#
- 17. MADRID F# MEETUP F# reduces code “noise” But you can use them • No curly braces for scope • No semicolons • Meaningful whitespace like Python • No return keyword if necessary C# F# Forward pipe operator
- 18. MADRID F# MEETUP Pattern Matching Match and deconstruct complex patterns with no hassle Wildcard Constant Empty list Guard The compiler warns you if you don’t cover all cases
- 19. MADRID F# MEETUP Pattern Matching Define your own active patterns Syntactic sugar
- 20. MADRID F# MEETUP Thinking sequentially (1) Use computation expressions (aka monads) to simplify complex programming workflows and simulate state machines Perform asynchronous operations as if they were synchronous
- 21. MADRID F# MEETUP Thinking sequentially (2) Define your own workflows easily Can return Some(value) or None ... and without With...
- 22. MADRID F# MEETUP Thinking sequentially (and 3) Parallelism made easy thanks to immutability and Async Erlang-like agents also available Parallel I/O Parallel CPU
- 23. MADRID F# MEETUP Domain Driven Design Programmers and non-programmers can Believe it! speak the same language
- 24. MADRID F# MEETUP Source
- 25. MADRID F# MEETUP Scripting With F# you can write both complex project and simple scripts There is a REPL too
- 26. FunScript F# to JavaScript with type providers MADRID F# MEETUP I ALREADY KNEW ALL THAT
- 27. MADRID F# MEETUP Killer Features: Measure Units Protect your number values for free! Combine them with other types Use generics The measure annotations disappear after compilation so they have no performance penalty The compiler prevents mistakes
- 28. FunScript F# to JavaScript with type providers MADRID F# MEETUP There are more killer features but let’s go directly to the crown jewel
- 29. MADRID F# MEETUP Killer Features: Type Providers Static typing on demand! Fsharp.Data Sergey Tihon’s blog
- 30. FunScript F# to JavaScript with type providers MADRID F# MEETUP I WANT NO ACADEMIC STUFF I WANNA MAKE REAL APPS!
- 31. MADRID F# MEETUP F# is multiplatform • .NET: Windows Desktop and Store, Windows Phone • Mono: Mac and Linux • Xamarin: Android and iOS • ASP.NET: Server • FunScript and WebSharper: Browser • GPU, FreeBSD... more at fsharp.org
- 32. FunScript F# to JavaScript with type providers MADRID F# MEETUP DEMO TIME
- 33. MADRID F# MEETUP Why F#? Why now? • Functional programming is booming • Great community, really open to newcomers • Everybody can contribute to the evolution of the language • Open source but backed by big companies oMicrosoft oXamarin • fun is a keyword!