Five Reasons to Move from C# to F#

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1 Five Reasons to Move from C# to F# JORGE FIORANELLI LEAD JORGEFIORANELLI

2 Who am I? Readify Lead Consultant - Sydney, Australia F# Sydney User Group (fsharpsydney.com) F# Workshop (fsharpworkshop.com) F# > I

3 Why F#?

4 Why F#?.Net Functional-First Full Support in VS Interoperable Multi Platform Open Source Great Syntax fsharp.org

5 Reason #1: Powerful Functions

6 Reason #1: Powerful Functions int Add(int x, int y) var return z = x x + + y; y; return z; Func<int,int,int> int Add(x, add(x, let Add(int y y) x y x, = x int + y y) let x + z y = x + y var let z z = x + y; return z z; int -> int -> int no let no camel parens instead curly no let semi and types case equals colons and of no return commas braces var In Out In Out Partial Application let result addone = add 1 2 //result: //addone: int = 3? -> int let result = addone 2 //result = 3 Pipelining let result = 2 customer addone > addone 2 > promotetovip > increasecredit Composition let addthree = addone >> addtwo let result = addthree 1 //result = 4

7 Reason #1: Powerful Functions [Fact] void Should_process_orders_when_they_are_approved() [<Fact>] let ``Should process orders when they are approved`` () =

8 Reason #1: Powerful Functions F# > I I F#

9 Reason #2: Great Types

10 Reason #2: Great Types class Customer private readonly string name; public Customer(string name) this.name = name; public string Name get return name; class type Customer(name: = string) = member this.name = name private public string readonly Name string name; type Customer = Name: string public get Customer(string string return Name name; name) this.name get return = name; Immutability Structural Equality public string Type Inference Name get return name; Class type generated readonly no primary instead curly of constructor property braces class field Record

11 Reason #2: Great Types Tuples Tuple<string, int> mytuple = GetNameAndAge(3); string name = mytuple.item1; int age = mytuple.item2; Tuple<string, let name, age = int> getnameandage mytuple = GetNameAndAge(3); GetNameAndAge(); 3 string let success, name = value mytuple.item1; = Int32.TryParse "42" int age = mytuple.item2; Options int GetCustomerAgeById(int id) Nullable<int> GetCustomerAgeById(int id) Customer GetCustomerById(int id) Nullable<Customer> GetCustomerById(int id) getcustomeragebyid (id: int) : int getcustomeragebyid (id: int) : Option<int> getcustomerbyid (id: int) : Customer getcustomerbyid (id: int) : Option<Customer>

12 Reason #2: Great Types Units of Measure var meters = 200; var kilometers = 30; var total = meters + kilometers; // 230! var [<Measure>] meters = type 200; m var [<Measure>] kilometers type= 30; km var let total meters = = meters 200<m> + kilometers; // 230!!! let kilometers = 30<km> let total = meters + kilometers // Error! Object Expressions var product = new Name = "Product1" ; return product; //? let product = new IProduct with member this.name = "Product1" member this.show () = printfn "%s" this.name

13 Reasons #1 #2 Powerful Functions Great Types

14 Reason #3: Pattern Matching

15 Reason #3: Pattern Matching enum Result Success, Error void Show(Result result) switch (result) case Result.Success: Console.WriteLine(":)"); break; case Result.Error: Console.WriteLine(":("); break; enum type Result = Discriminated Success of int quotient: int Union * remainder: int Success, Error of string Exception Error void let show ( Pieces _ ) Show(Result result = result) = match switch result (result) with void switch Success Show(Result case (result) (q,0) (q,r) -> Result.Success: -> Console.WriteLine(":)") result) printfn -> when printfn q > 1 %i" "%i -> Some printfn r %i" q r "%i pieces" q Success Error _ -> case None e -> m (q,r) Console.WriteLine(":)"); -> Result.Success: Console.WriteLine(":(") printfn -> printfn "%s" %s" e.message "%i m %i" q r Error switch case e (result) Console.WriteLine(":)"); break; -> Result.Success: printfn "%s" e.message let show show (Success case result Console.WriteLine(":)"); break; Result.Error: = 2) show Success // //:):) 2 show match show (Success (Error case result break; Console.WriteLine(":("); Result.Success: Result.Error: (quotient=2, "Error with show message") remainder=0)) Error // //:( :( Error // message 2 pieces show Pieces (Success caseq Console.WriteLine(":)"); Console.WriteLine(":("); break; Result.Error: ->(quotient=2, printfn "%i remainder=1)) pieces" q // 2 1 show Success (Error (q,r) Console.WriteLine(":("); break; (Exception("Error"))) -> printfn "%i %i" q r // Error Error case e break; -> Result.Error: printfn "%s" e.message Console.WriteLine(":("); break;

16 Reasons #1 #2 #3 Powerful Functions Great Types Pattern Matching

17 Reason #4: Type Providers

18 Reason #4: Type Providers Json TypeProvider Json Data F# Types Sql TypeProvider Sql Data Csv TypeProvider Csv Data

19 Reason #4: Type Providers Id,Name,IsVip,Credit 1,Customer1,false,0.0 type Customer = CsvProvider<"sample.csv"> let customers = Customer.Load "real.csv" customers.rows > Seq.iter (fun r -> printfn "%s: $%g" r.name r.credit) Id,Name,IsVip,Credit 1,Customer1,false,0.0 2,Customer2,false,10.0 3,Customer3,false,30.0 4,Customer4,true,50.0 type EntityConnection = SqlEntityConnection <ConnectionString=cs, Pluralize=true> let context = EntityConnection.GetDataContext () let customers = query for customer in context.customers do select customer.name Data

20 Reason #4: Type Providers Csv EF Json Azure Storage Xml Excel OData Linq2Sql SQL SQLClient Reflection World Bank R Freebase WMI Hadoop WSDL and more

21 Reasons #1 #2 #3 #4 Powerful Functions Great Types Pattern Matching Type Providers

22 Reason #5: Computation Expressions

23 Reason #5: Computation Expressions let x = iseven 1 let y = iseven 2 x && y Value: false Value: true Result: false log let! x = iseven 1 let! y = iseven 2 return x && y Value: false Value: true Result: false type LogBuilder() = member this.bind (value, continuation) = printfn "Value: %b" value continuation value member this.return value = printfn "Result: %b" value value let log = LogBuilder()

24 Reason #5: Computation Expressions Async Expression let readasync (file: (file: string) string) = = async use reader = new StreamReader(file) let! content = = reader.readtoend reader.asyncreadtoend () () content > printfn "Content: %s" EF Type Provider Query Expression let result = query for student in db.student do where (student.studentid > 4) select student MBrace Cloud let first = cloud return 15 let second = cloud return 27 cloud let! x = first let! y = second return x + y

25 Reasons #1 #2 #3 #4 #5 Powerful Functions Great Types Pattern Matching Type Providers Computation Expressions Partial Application Pipelining Composition Spaces in Names Classes Records Tuples Options Units of Measure Object Expressions Discriminated Unions Pattern Matching Active Patterns CSV EF Log Async Query Cloud

26 Thank you! Jorge Resources fsharp.org Real-World Functional Programming By Tomas Petricek Try F#: tryfsharp.org Scott Wlaschin fsharpforfunandprofit.com fpbridge.co.uk/why-fsharp.html github.com/jorgef/ fivereasons Skills Matter: skillsmatter.com (tag: f#) Community for F#: c4fsharp.net F# Workshop: fsharpworkshop.com

Methods. Contents Anatomy of a Method How to design a Method Static methods Additional Reading. Anatomy of a Method

Methods. Contents Anatomy of a Method How to design a Method Static methods Additional Reading. Anatomy of a Method Methods Objectives: 1. create a method with arguments 2. create a method with return value 3. use method arguments 4. use the return keyword 5. use the static keyword 6. write and invoke static methods