C# Func<> - looking for an explanation - not a solution

user_6502723 0
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i am using Math.net, among other methods i use integration, the integration function i use is defined as foloows:

public static double IntegrateComposite(
  Func<double, double> f,
  double intervalBegin,
  double intervalEnd,
  int numberOfPartitions)

yet, my call syntax is:

p = IntegrateComposite(
tau => MyFunction(r, tau, appCfg, Ta, Da) * ProbDensity(tau), 
lowLim, hiLim,  32)

My function is better defined as Func<double, double, double, double, double, double> and not the above Func<double, double>, still everything works fine Why?

c#
3 Answers

This is your the function you pass in, the only input argument is tau. 

tau => MyFunction(r, tau, appCfg, Ta, Da) * ProbDensity(tau)

The other varibales r, appCfg, Ta, Da are 'closed over' by a closure

user_657470

Func<double, double> means

a function which takes 1 argument of type double in, and returns double

That's exactly what your arrow function does, no matter how many external variables are involved into calculation.

user_32186920

Func<T1, T2, T3..., T(n), TResult> is a type that represents a method which takes (n) number of parameters with specified types (could be 0), and returns an object of type TResult.

By Func<double, double>, it specifies that it must be a method which takes one double as a parameter and return a double.

In this example, Lambda function is used (which also can be represented by Func). 

tau => {return MyFunction(r, tau, appCfg, Ta, Da) * ProbDensity(tau)},

The only parameter you pass into the lambda function is tau, which can be seen on the left hand side of the arrow. Other variables such as r, tau, appCfg... are captured variables.

Another example of generic delegates: (obj, e) => {Console.WriteLine(obj)} is passed two variables named obj and e. Unlike your example, It returns nothing. This is represented as Action<T1, T2> which represents a method that returns nothing.

user_104845670
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