c++ for_each 用法_小鍵233-CSDN博客

傳入參數

• 要傳入參數給global function ,需要使用 ptr_fun() 這個 function adapter 將global function 轉成function object , 然后再用bind2nd() 將參數bind成一個function object。（這句話好拗口）

void fun(int i, const char* str) {cout<<str<<i<<endl; }int main() {int a[] = { 1, 2, 3, 4};vector<int> v(a, a+sizeof(a)/sizeof(int));for_each(v.begin(), v.end(), bind2nd(ptr_fun(fun), "Element:")); } #include <iostream> #include <vector>template<class T> struct plus2{void operator()(T& x){x += 2;} };//template <class T> void plus3_fun(int& x){x += 3; // std::cout << x << " "; }void fun(int i,const char* str){std::cout << str << "->" << i << std::endl; }int main(){ // int ia[] = {22,30,20,34,45,64,34,56,75,34}; // std::vector<int>iv(ia,ia+(sizeof (ia) / sizeof (int))); // for (int i : iv) { // std::cout << i << ' '; // } // std::cout << std::endl; // std::cout << iv.size() << ' '; // std::cout << std::endl; //std::for_each(iv.begin(),iv.end(),plus2<int>()); // std::for_each(iv.begin(),iv.end(), std::bind2nd(std::ptr_fun(fun),"Hello world")); // for (int i : iv) { // std::cout << i << ' '; // }int ia[] = {1,2,100,200};std::vector<int>arr(ia,ia+(sizeof (ia)/sizeof (int)));//移除所有小于100的元素//bind2nd(判斷條件,標準) 判斷條件 標準//bind1nd(判斷條件,標準) 標準 判斷條件/** std::bind1nd(std::less<int>(),100)) 100 < x* std::bind2nd(std::less<int>(),100)) x < 100*/ // arr.erase(std::remove_if(arr.begin(),arr.end(),std::bind2nd(std::less<int>(),100)),arr.end()); //100 200 // arr.erase(std::remove_if(arr.begin(),arr.end(),std::bind1st(std::greater<int>(),100)),arr.end());// arr.erase(std::remove_if(arr.begin(),arr.end(),std::bind2nd(std::greater<int>(),100)),arr.end()); // arr.erase(std::remove_if(arr.begin(),arr.end(),std::bind1st(std::less<int>(),100)),arr.end()); //1 2 100//刪除小于等于100的元素arr.erase(std::remove_if(arr.begin(),arr.end(),std::not1(std::bind2nd(std::greater<int>(),100))),arr.end());for(auto i : arr){std::cout << i << " ";} }

ptr_fun

• C++11棄用 被更通用的std::function 和 std::ref替代

#include <iostream> #include <vector> #include <functional> #include <algorithm>bool isvowel(char c){return std::string("aeiouAEIOU").find(c) != std::string::npos; }int main(){std::string s = "Hello world!";std::copy_if(s.begin(),s.end(),std::ostreambuf_iterator<char>(std::cout),std::not1(std::ptr_fun(isvowel))); }//Hll wrld!

std::function函數

• std::function - cppreference.com?

#include <iostream> #include <vector> #include <functional> #include <algorithm>struct Foo{Foo(int num):num_(num){};void print_add(int i)const {std::cout << num_ + i << std::endl;}int num_; }; void print_num(int i){std::cout << i << '\n'; } struct print_Num{void operator()(int i){std::cout << i << '\n';} };int main(){//store a free functionstd::function<void(int)>f_display = print_num;f_display(-9);//strore a lambdastd::function<void()> f_display_42 = [](){ print_num(43);};f_display_42();//store the result of a call to std::bindstd::function<void()>f_display_31337 = std::bind(print_num,31337);f_display_31337();//store a call to a member functionstd::function<void(const Foo&,int)>f_add_display = &Foo::print_add;const Foo foo(300000);f_add_display(foo,1);//store a call to a member function and objectusing 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 ptrstd::function<void(int)>f_add_display3 = std::bind(&Foo::print_add,&foo,_1);f_add_display3(3);//store a call to a function objectstd::function<void(int)>f_display_obj = print_Num();f_display_obj(18); }

參考鏈接

• bind1st bind2nd的使用_simahao的專欄-CSDN博客_bind2nd
• C++ STL std::ptr_fun() 函數說明 - 簡書
• C++中string::npos的一些用法總結_竭盡全力的專欄-CSDN博客

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