func 函数的嵌套 C delegate

给一个数n，如果能被3整除就print Func3(n)，如果能被5整除就print Func5(n)，如果能被3和5整除就print Func3(Func5(n)).
follow-up, 把上面的代码改成general的，如这时有{3，5，7}，能被3和7整除的话就print Func3(Func7(n))，能被3，5，7都整除print Func3(Func5(Func7(n)))

You have an incredible number of choices to achieve delegates in C++. Here are the ones that came to my mind.

Option 1 : functors:

A function object may be created by implementing operator()

struct Functor { // Normal class/struct members

 int operator()(double d) // Arbitrary return types and parameter list
 {
      return (int) d + 1;
 }

};

// Use: Functor f; int i = f(3.14);

Option 2: lambda expressions (C++11 only)

// Syntax is roughly: [capture] (parameter list) -> return type {block} // Some shortcuts exist auto func = -> double { return 2*i/1.15; }; double d = func(1);

Option 3: function pointers

int f(double d) { ... } typedef int (*MyFuncT) (double d); MyFuncT fp = &f; int a = fp(3.14);

Option 4: pointer to member functions (fastest solution)

See Fast C++ Delegate (on The Code Project).

struct DelegateList { int f1(double d) { } int f2(double d) { } };

typedef int (DelegateList::* DelegateType)(double d);

DelegateType d = &DelegateList::f1; DelegateList list; int a = (list.*d)(3.14);

Option 5: std::function

(or boost::function if your standard library doesn't support it). It is slower, but it is the most flexible.

#include <functional>
std::function<int(double)> f = [can be set to about anything in this answer]
// Usually more useful as a parameter to another functions

Option 6: binding

Allows setting some parameters in advance, convenient to call a member function for instance.

struct MyClass { int DoStuff(double d); // actually a DoStuff(MyClass* this, double d) };

std::function f = std::bind(&MyClass::DoStuff, this, std::placeholders::_1); // auto f = std::bind(...); in C++11

func 函数的嵌套