Higher order functions in C#
C# is not a functional language
...but it is a gateway drug to functional programming.
ready?
first class functions
functions can be assigned to variables
to be passed around
at a language level
Does [language] support first-class functions?
does c# support first-class functions?
YES
higher-order functions
a function that brings in a function
a function that returns a function
at a function level
Is this a higher-order function?
c# 2 (2005)
generics
anonymous methods
delegates
C# 3 (2007)
type inference
anonymous types
extension methods
lambdas
expressions
first-class things
public void DoSomethingWithFruit(){int numberOfApples = 6;DoSomethingWithApples(numberOfApples);}
public void MakePie(string flavour){UseFlavour(flavour);}string pieFlavour = "Steak n Cheese";MakePie(pieFlavour);
action
A class that represents a function
public void WhistleJauntyTune(){// let the whistling commence...}Action whistle = WhistleJauntyTune;// call the actionwhistle();
action<t>
Arguments!
public void JumpAround(int numberOfTimes){// jump up jump up and get down}Action<int> jump = JumpAround;jump(17);
action<t1, t2, ...>
As argumentative as you like!
public void Something(int i, string s, double d){// something something all the things...}var something = Something;something(1, "1", 1.0);
Func<t>
For returning things
public int TheAnswer(){return 42;}Func<int> answer = TheAnswer;var a = answer();
func<t, tR>
TR: Response Type
public string DoThisThing(int number){return number.ToString();}Func<int, string> thisThing = DoThisThing;string s = thisThing(3); // s == "3"
demo
The rest of the talk was in VS