public static void Main(string[] args)
{
// Delegate in .NET are actually "multicast": they can point to multiple functions at the same time.
// When the delegate is invoked, each of the functions it points to are called in turn.
Action <string> phrases = SayHello;
// the += operator can append another function of the delegate type
phrases += SayGoodbye;
// When we invoke phrases, the two functions will be called synchronously.
phrases("Neal");
// Output?
// What about nonvoid return types? How can we call two functions that both return something, if
// function calls can only return one value.
Func <double, double> f = Math.Abs;
f += Math.Floor;
// Func<double,double> returns a double when invoked...
double result = f(-10.5);
// ... but which function is actually returned?
Console.WriteLine($"result: {result}");
// Declare a Stack variable.
IntStack s = new IntStack();
// I want to be informed whenever an item is added to this stack, so I "subscribe" to the
// ItemAdded event.
s.ItemAdded += Stack_ItemAdded;
// I also want to know when something is removed.
s.ItemRemoved += Stack_ItemRemoved;
// Now when I call s.Push, what happens?
s.Push(100);
s.Push(200);
s.Pop();
// How is this different than just calling Stack_ItemAdded from within the Stack.Push method?
// Why bother with this approach?
}
public static void Stack_ItemRemoved(IntStack stack, int item)
{
Console.WriteLine($"{item} was just removed from the stack, which now has {stack.Count} elements");
}
public static void Stack_ItemAdded(IntStack stack, int item)
{
Console.WriteLine($"{item} was just added to the stack, which now has {stack.Count} elements");
}
