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Functional Programming
This document discusses functional programming concepts and how they can be applied using C#. It introduces functional programming, defining it as a style where functions are treated as values. It covers functional programming concepts like immutability, recursion, and declarative programming. It then demonstrates how functional programming principles can be used in C# through techniques like Func and Action generics, LINQ queries, closures, currying, and parallelism using TPL and Rx. Resources for learning more about functional programming in C# and other languages are provided.
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Functional Programming
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- 2. Who am I?RyanRileyCatapult Systems HoustonBlog: http://wizardsofsmart.netGitHub: http://github.com/panesofglassTwitter: @panesofglass
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- 4. 1. Functional ProgrammingConcepts
- 5. Functional programming isjust a style.
- 6. Treat functions asvalues.
- 7. What is afunction?A function, as in math.(In particular, as in lambda calculus.)((Ask Jeff Odell.))
- 8. Follow the Arrowsaddx y has a type of int -> int -> intIn C#, this could be Func<int, int, int>(Actually, thatâs Func<int,<Func<int, int>>>. Weâll see why in a momentâŚ.)
- 9. Functions are values,too..NET 1.0 => delegates.NET 2.0 => anonymous delegates + generics.NET 3.0 => lambdasHigher-order functions accept a function as a parameter.
- 10. ImmutabilityNO side effects!NOstate!NO I/O! Functions take an input and return a resultImage from One Year Bible Blog
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- 13. AdvantagesVery easy toreason aboutConcurrency friendlyEasy to compose:doubleSq x = square(double(x))doubleSq = double . squareFoundation of Domain Specific Languages
- 14. DisadvantagesToo much recursioncan overflow the stack (without tail-call optimization, or TCO)High memory consumption from creating so many objects âŚ
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- 16. Referential transparencyReplace afunction with its valueEfficiency with caching (a.k.a. memoization)Easier for programmers to understandâ´ Easier to reuse and test
- 17. So what?Mooreâs Lawis failing.Multiple CPUs / cores is the future.Controlling mutable state in concurrency is very hard âŚunless you have no mutable state!
- 18. Also,âMock objects anddependency injection are just for people who donât know math.â*~ Erik Meijer, Microsoft* See the Silverlight Toolkit for test examples.
- 19. 2. Play thatFuncâyMusic C#
- 20. Func & ActionDefineyour functions.Generics are important.Type-safety over many types.
- 21. Lists everywhere!Functional languageslike Lisp build entirely on lists and maps (i.e. Dictionaries).Feel like youâve seen this before?
- 22. Also by ErikMeijer!LINQ!Implementation of common functional programming functions over lists via IEnumerable.Select => mapWhere => filterAggregate => fold / reduceSelectMany => bind / fmap, or âmap then flattenâ
- 23. This means youare probably already using FP!
- 24. Take it furtherFunctionsas dataClosures => Capture external state for laterCurrying + Partial application =>Reduce dependenciesMemoization => Run it again later
- 25. DemoCurrying and Partialapplication
- 26. Make it concurrentTaskParallel Library (PFx)Reactive Extensions (Rx)PLinq => Parallel LINQ
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- 28. What didnât wecover?Many more functional operators (LINQ)Managing mutable state from the environmentLINQ to Observables, Continuations, etc.The âMâ word
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- 30. Books ân BlogsReal-WorldFunctional ProgrammingPFx Team BlogRx Team BlogMatthew Podwysockiâs Weblog
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- 32. VideosFunctional Programming Fundamentals(Channel9 Lecture Series)
- 33. LanguagesMore F# =>http://c4fsharp.groups.live.comMore Clojure and IronScheme => http://hdlug.groups.live.com
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