[转]c++ function使用方法
原帖:https://blog.csdn.net/myRealization/article/details/111189651
boost源码剖析之:泛型函数指针类boost::function https://blog.csdn.net/pongba/article/details/1560773
#include <functional> #include <iostream> struct Foo { Foo(int num) : num_(num) {} void print_add(int i) const { std::cout << num_ + i << '\n'; } int num_; }; void print_num(int i) { std::cout << i << '\n'; } struct PrintNum { void operator()(int i) const { std::cout << i << '\n'; } }; int main() { // store a free function std::function<void(int)> f_display = print_num; f_display(-9); // store a lambda std::function<void()> f_display_42 = []() { print_num(42); }; f_display_42(); // store the result of a call to std::bind std::function<void()> f_display_31337 = std::bind(print_num, 31337); f_display_31337(); // store a call to a member function std::function<void(const Foo&, int)> f_add_display = &Foo::print_add; const Foo foo(314159); f_add_display(foo, 1); f_add_display(314159, 1); // store a call to a data member accessor std::function<int(Foo const&)> f_num = &Foo::num_; std::cout << "num_: " << f_num(foo) << '\n'; // store a call to a member function and object using std::placeholders::_1; std::function<void(int)> f_add_display2 = std::bind(&Foo::print_add, foo, _1); f_add_display2(2); // store a call to a member function and object ptr std::function<void(int)> f_add_display3 = std::bind(&Foo::print_add, &foo, _1); f_add_display3(3); // store a call to a function object std::function<void(int)> f_display_obj = PrintNum(); f_display_obj(18); auto factorial = [](int n) { // store a lambda object to emulate "recursive lambda"; aware of extra overhead std::function<int(int)> fac = [&](int n) { return (n < 2) ? 1 : n * fac(n - 1); }; // note that "auto fac = [&](int n) {...};" does not work in recursive calls return fac(n); }; for (int i{5}; i != 8; ++i) std::cout << i << "! = " << factorial(i) << "; "; std::cout << '\n'; }
Possible output:
-9 42 31337 314160 314160 num_: 314159 314161 314162 18 5! = 120; 6! = 720; 7! = 5040;