techdaysnl 2015 - f# for c# developers
TRANSCRIPT
F# for C# developersRonald Harmsen
Why?
“First, it’s almost certainly true that functional programming is the next big thing. “
Robert C. Martin
“Object oriented programming makes code understandable by encapsulating moving parts. Functional programming makes code understandable by minimizing moving parts.“
Michael Feathers
“F# is excellent at concisely expressing business and domain logic.Developers trying to achieve explicit business logic within an Application may opt to express their domain in F# with the majority of plumbing code in C#.”
Functional programming
• Declarative
• Clearity
• Composability
• Immutability
Characteristic Imperative approach Functional approach
Programmer focusHow to perform tasks (algorithms)
how to track changes in state.
What information is desired and what transformations are required.
State changes Important. Non-existent.
Order of execution Important. Low importance.
Primary flow controlLoops, conditionals, and function
(method) calls.Function calls, including recursion.
Primary manipulation unit
Instances of structures or classes.Functions as first-class objects
data collections.
Characteristic C# F#
Programmer focusHow to perform tasks (algorithms)
how to track changes in state.
What information is desired and what transformations are required.
State changes Important. Non-existent.
Order of execution Important. Low importance.
Primary flow controlLoops, conditionals, and function
(method) calls.Function calls, including recursion.
Primary manipulation unit
Instances of structures or classes.Functions as first-class objects
data collections.
Why F# ?
• Functional-first
• Very strong type inference
• Integrate with other .NET technologies
• Windows, Web, Xamarin iOS & Android, Linux
The functional language in .NET
FunctionsEverything is a function
let a = 10
int a () {return
10;}
let sum a b = a + b
int sum (int a, int b) {return a + b;
}
Composability
public static class Calc {
public static decimal Square(decimal n){
return n * n;}
public static decimal MultiplyByPi(decimal n) {
return n*3.14m;}
public static decimal AreaOfCicle(decimal r){
return MultiplyByPi(Square(r));}
}
module Calclet square n = n ** 2.0
let multiplyByPi n = n * 3.14
let areaOfCircle r = multiplyByPi (square (r))
let square n = n ** 2.0let multiplyByPi n = n * 3.14
let areaOfCircle r = r |> square |> multiplyByPi
let square n = n ** 2.0let multiplyByPi n = n * 3.14
let areaOfCircle r = square >> multiplyByPi
Types: tuples
type person = name * age
Types: record
type person = { name: string; age : int
}
Types: discriminated unions
type Employee =| Developer| Manager
Types: discriminated unions
type Employee =| Developer of Person| Manager of Person
DEMOTypes in F#
Pattern matching
let data = (“Den Haag”, 070)let city, areanumber = data
Pattern matching
let x = 9match x with
| 1 -> printfn “the number is one”| num when num < 10 ->
printfn “number is below 10”| _ -> printfn “number is above 10”
Option
NULL -> NullReferenceException
Option
type Option<'a> = | Some of 'a | None
Measures
[<Measure>] type m[<Measure>] type s
let distance = 10.0<m>let time = 2.0<s>
let speed = distance / time
match speed with | x when x < 5.<m/s> -> printfn "Slow" | _ -> printfn "Fast"
Why F#?
• Compact, concise and readable syntax
• Clearity, also readable by domain experts
• Very good for modelling domain entities & value objects
• Perfect match for processing sets of data
• Async made easy through immutability
Demo
More interesting stuff
Lists vs SequencesType providers
My other session : “Domain Driven Design with F#”, Kilimanjaro 11.30
Rick’s session : “C#: Raise the bar with Functional & Immutable constructs”Pacific, 12.15
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Laat ons weten wat u van de sessie vindt!Scan the QR Code via de TechDays App.
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