An Introduction to F Sushant Bhatia aboutdev com

An Introduction to F# Sushant Bhatia @aboutdev. com aboutdev@gmail. com

Why learn F#?

Overview §Tour of F# in Visual Studio 2011 §Fundamentals of F# §Functional Programming §Examples

DEMO F# in Visual Studio 2011

Fundamentals of F#

Core Types Signature Name Description Example Unit () int, float Concrete Type 10, 6. 04 ‘a, ‘b Generic Type ‘a -> ‘b Function Type ‘a * ‘b Tuple Type Ordered collection (1, 2), (“ten”, of values “soup”) ‘a list List Type List of values [1; 2; 3], [1. . 3] ‘a option Option Type Optional value Some(3), None fun x -> x + 1

Modules & Namespaces §Default -> anonymous module §Nest Modules §Namespace

Pipe Forward §Pass results of first function to second §Benefit §Chain functions together §Type inference [1. . 10] |> List. map (fun x -> x * x) |> List. iter (printfn "%i")

Pattern Matching § Series of rules that will execute if a pattern matches the input. § Switch on Steroids

Discriminated Unions §Type § 1 of a set of possible values §Used for complex data structures

Functional Programming

What is Functional Programming? A function is a rule that associates to each x from some set X of values, a unique y from another set Y of values. If f is the name of the function, y = f ( x ) f : X → Y

Functional programming is a programming paradigm that treats computations as the evaluation of mathematical functions and avoids state and mutable data. [Wikipedia]

§ All programs and procedures are functions and clearly distinguish incoming values from outgoing values § There are no variables or assignments – variables are replaced by parameters § There are no loops – replaced by recursive calls § The value of a function depends only on the value of its parameters and not on the order of evaluation or the execution path that led to the call § Functions are first-class values (viewed as values themselves, computed by other functions and can be parameters to functions) [Programming Languages. Kenneth C Louden]

1. First Class Functions 2. Higher Order Functions 3. Pure Functions 4. Recursion / Tail Recursion 5. Currying

1. First Class Functions a) Bind an identifier to a function definition let sqr = fun n -> n * n b) Store functions in data structures let a. Tuple = (sqr, fun n -> n + n) let a. List = [sqr, fun n -> n + n]

2. Higher Order Functions a) Pass function as an argument let data = List. map (fun n -> n * n) [ 1; 2; 3; 4; ] b) Return function as value of function let sqr. List = let fun. Sqr = fun lst -> List. map (fun a -> a * a) lst fun. Sqr

3. Pure Functions a) No Side Effects / Referential transparency b) Caching optimizations (memoization) c) No Data Dependency = order of execution is independent and can be parallel (thread-safe)

4. Recursion / Tail Recursion a) Iteration through recursive invocation let rec factorial x = if x <= 1 I then 1 I else let rec. Result = factorial (x-1 I) let result = x * rec. Result result b) Tail recursion – Accumulators let factorial. Tail x = let rec tail. Rec. Fact x acc = if x <= 1 I then acc else tail. Rec. Fact (x-1 I) (acc * x) tail. Rec. Fact x 1 I

5. Currying let add x y = x + y let add. To. Ten = add 10 add. To. Ten 5

1. Type Provider – Netflix 2. Units of Measure 3. Async / Parallel Demo

Examples – Project Euler

1. Programming F# - Chris Smith 2. Beginning F# - Robert Pickering 3. Expert F# - Don Syme 4. 5. 6. 7. http: //blogs. msdn. com/b/dsyme http: //en. wikibooks. org/wiki/Programming: F_Sharp http: //projecteuler. net/ http: //fdatamining. blogspot. com/2009/12/f-onlinevideos. html 8. http: //www. tryfsharp. org/Tutorials. aspx 9. http: //fssnip. net/ How to Learn F#

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