1. dotnetConf
11/19/2018 6:01 AM
© 2016 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

2. F# for the Practical Developer
dotnetConf
11/19/2018 6:01 AM
F# for the Practical Developer
Phillip Carter
Program Manager, Visual F#
© 2016 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

3. A Brief Introduction to F#
dotnetConf
11/19/2018 6:01 AM
A Brief Introduction to F#
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4. A Functional First, Multi-Paradigm Language
dotnetConf
11/19/2018 6:01 AM
A Functional First, Multi-Paradigm Language
Mature, Open Source, Cross-platform
Strongly and Statically-typed
But with type inference, is less code! More on that later.
Supports scripting and REPL-driven work
Quickly prototype a proof of concept, or script an ad-hoc solution
Powerful Core Libraries with Fsharp.Core
Async Programming, Message-Passing, Data Wrangling, Sequence Processing, and more
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

5. Let’s see some code! dotnetConf 11/19/2018 6:01 AM
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

6. A Functional First, Multi-Paradigm Language
dotnetConf
11/19/2018 6:01 AM
A Functional First, Multi-Paradigm Language
Functional Programming
Immutability by default
Mutability is explicit rather than always present
let mutable x = … // x is now mutable
Less surprises in program behavior
“Pit of Success” when your codebase gets larger
Correct designs are natural; bug-prone ones aren’t
First-Class Functions
Functions can be passed as parameters to other functions
let startsWithVowel firstChar = Seq.contains firstChar “AEIOUaeiou” // Scan vowel list for a match
let toPigLatin name = if (startsWithVowel name.[0]) then name + “yay”
else String.Concat(name.SubString(0), name.[0], “ay”) // Use a .NET string method!
let makeThemPigLatin names = names |> List.map toPigLatin // passing toPigLatin function as an argument
let pigLatinFruit = [“Apple”; “Banana”] |> makeThemPigLatin
printfn “After translation: %A” pigLatinFruit // prints ’After Translation: [“Appleyay”; “ananaBay”]’
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

7. A Functional First, Multi-Paradigm Language
dotnetConf
11/19/2018 6:01 AM
A Functional First, Multi-Paradigm Language
Functional Programming
Powerful type system
Type inference means significantly less boilerplate code
let format s = sprintf “custom formatting! %s” s // infers the ‘s’ parameter and return type as string
F# types allow you to push certain runtime behaviors into compile-time
Example: Account for all cases with the Option<`T> type when parsing
module Parsing =
let private tryParseWith tryParseFunc s =
match (tryParseFunc s) with
| true, v -> Some v // Success! It parsed and there’s a value
| false, _ -> None // Failed! Callers MUST account for this case now
let parseDateTime s = tryParseWith System.DateTime.TryParse s
open Parsing
// Returns an Option<DateTime>, which you must pattern match at COMPILE TIME to use!
parseDateTime “ ”
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

8. A Functional First, Multi-Paradigm Language
dotnetConf
11/19/2018 6:01 AM
A Functional First, Multi-Paradigm Language
Functional Programming
Powerful type system
Ability to easily represent more complex information with Discriminated Unions
type BinarySearchTree<‘T> =
| EmptyTree
| Node of ‘T * BinarySearchTree<‘T> * BinarySearchTree<‘T>
Units of Measure for numerical type safety
[<Measure>] type Minute
[<Measure>] type Second
// Use type annotation to inform the compiler of the unit of measure
let addMinutes (currentTime: int<Minute>) (mins: int<Minute>) = currentTime + mins
addMinutes 40<Minute> // Compile Error – a good thing
addMinutes 40<Minute> 12<Second> // Compile Error – a good thing
addMinutes 40<Minute> 12<Minute> // Success!
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

9. A Functional First, Multi-Paradigm Language
dotnetConf
11/19/2018 6:01 AM
A Functional First, Multi-Paradigm Language
Object-Oriented Programming
Full OOP Support
Classes, Interfaces and Abstract Classes, Inheritance, Generics
type Vector2D(dx: float, dy: float) =
let length = sqrt (dx*dx + dy*dy) // private function; not visible outside Vec2
member val DX = dx with get, set // Public auto-property
member this.DY = dy // Immutable public property
member private this.Length = length // Immutable private property
member this.Scale(k) = Vec2D(k + this.DX, k * this.DY) // Public method
type ILogger =
// Interfaces are types with only function signatures
abstract member Log: string -> string // Takes a string; returns a string
type Car(engine, fourWheels) =
inherit Vehicle(engine) // `inherit` is how you derive a base class …
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

10. A Functional First, Multi-Paradigm Language
dotnetConf
11/19/2018 6:01 AM
A Functional First, Multi-Paradigm Language
Object-Oriented Programming
Full OOP Support
Object Expressions
Implement interfaces on the fly, as you need them
Example use case: mocking a simple interface without needing a mocking library
open Xunit // From the Xunit NuGet package
open MyProject.Services // A namespace with a function called ‘getAndDeserializeJson’
let mockJsonService =
{ new IGetJsonService with // ‘new IInterface with …’ is the Object Expression
member this.getJson url }
[<Fact>]
let ``Service Deserializes number correctly``() =
let fakeUrl = “
let result = getAndDeserializeJson mockJsonService fakeUrl
Assert.Equal(42, result)
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

11. A Functional First, Multi-Paradigm Language
dotnetConf
11/19/2018 6:01 AM
A Functional First, Multi-Paradigm Language
Runs on .NET and it’s Supported
A .NET language
Access to every amazing .NET library
Can call C# or VB code from F#
Can call F# code from C# or VB
Tooling in Visual Studio
Intellisense, Reactoring, and All-around Visual Studio Goodness
Same amazing debugging support you get with C# and VB
Intensely devoted OSS community
Language and Compiler is OSS
Vast collection of powerful 3rd party libraries and tools
Supported and Actively Developed by Microsoft
Language and tooling developed on GitHub (github.com/Microsoft/VisualFSharp)
OSS contributions welcome!
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

12. Demo: Extending a Web App
dotnetConf
11/19/2018 6:01 AM
Demo: Extending a Web App
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13. There’s so much more Amazing features I didn’t cover
dotnetConf
11/19/2018 6:01 AM
There’s so much more
Amazing features I didn’t cover
Computation Expressions
A general purpose mechanism for managing data, control, and side effects
Example – async programming:
open FSharp.Data
let fetchHtmlAsync url = async { return! Http.AsyncRequestString url }
Messages and Agents
MailboxProcessor<‘T> - an actor model for concurrent programming built into FSharp.Core
Message passing feels like it’s built right into the language`
Type Providers
Component which provides types, properties, and members for consuming data
“Automatic” access to any data if you have a type provider
Json, SQL, CSV, Yaml, XML, and so many more
Huge OSS community involvement in building tons of high quality type providers
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

14. dotnetConf
11/19/2018 6:01 AM
© 2014 Microsoft Corporation. All rights reserved. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.