Adapted from HPCSE I notes, Prof. Troyer.
The new c++ standard c++11 introduced several useful and tricky features.
std::function
Great for callbacks, collection of callbacks, and threading. Support lambda functions.
[cpp]//From http://www.hankcs.com/program/cpp/c11-std-function-usage.html
#include <iostream>
#include <map>
#include <functional>
using namespace std;
// 普通函数
int add(int i, int j) { return i + j; }
// lambda表达式
auto mod = [](int i, int j){return i % j; };
// 函数对象类
struct divide
{
int operator() (int denominator, int divisor)
{
return denominator / divisor;
}
};
///////////////////////////SubMain//////////////////////////////////
int main(int argc, char *argv[])
{
// 受限的map
map<char, int(*)(int, int)> binops_limit;
binops_limit.insert({ ‘+’, add });
binops_limit.insert({ ‘%’, mod });
// 错误 1 error C2664: “void std::_Tree<std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,false>>::insert(std::initializer_list<std::pair<const _Kty,_Ty>>)”: 无法将参数 1 从“initializer-list”转换为“std::pair<const _Kty,_Ty> &&”
// binops_limit.insert({ ‘%’, divide() });
// 更灵活的map
map<char, function<int(int, int)>> binops =
{
{ ‘+’, add },
{ ‘-‘, minus<int>() },
{ ‘*’, [](int i, int j){return i – j; } },
{ ‘/’, divide() },
{ ‘%’, mod },
};
cout << binops[‘+’](10, 5) << endl;
cout << binops[‘-‘](10, 5) << endl;
cout << binops[‘*’](10, 5) << endl;
cout << binops[‘/’](10, 5) << endl;
cout << binops[‘%’](10, 5) << endl;
system("pause");
return 0;
}
///////////////////////////End sub//////////////////////////////////[/cpp]
auto
[cpp]auto x=3.141+5;
auto y=call_to_function_with_horrible_return_type();
[/cpp]