c/c++ 标准库 bind 函数详解

auto newCallable = bind(callbale, arg_list);

auto idx = find_if(svec.begin(),svec.end(),bind(check_size, _1, 6));

//_1,_n定在std::placeholders里面
using namespace std::placeholders;

//g是以个有2个参数的可调用对象
auto g = bind(func, a, b, _2, c, _1);//func是有5个参数的函数

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <functional>
using namespace std;
//_1,_n定在std::placeholders里面                        
using namespace std::placeholders;
bool check_size(const string &s, string::size_type sz){
 return s.size() >= sz;
}
bool shorter(const string &a, const string &b){
 return a.size() < b.size();
}
ostream& print(ostream& os, const string &s, const char &c){
 //c = ',';                                  
 return os << s << c;
}
int main(){
 /*                                      
 //用bind实现了和lambda一样的功能                       
 vector<string> svec{"aab","d","aa","bb","e","bbb"};              
 stable_sort(svec.begin(),svec.end(),[](const string &a, const string &b){   
   return a.size() < b.size();                        
  });                                     
 string::size_type sz = 3;                           
 auto idx = find_if(svec.begin(),svec.end(),bind(check_size, _1, sz));     
 cout << *idx << endl;                             
 idx = find_if(svec.begin(),svec.end(),[sz](const string &s){         
   return s.size() >= sz;                          
  });                                     
 cout << *idx << endl;                             
 */
 /*                                      
 //用bind改变原来函数的参数的位置                       
 //升序                                    
 vector<string> svec{"aab","d","aa","bb","e","bbb"};              
 sort(svec.begin(), svec.end(), shorter);                   
 for(auto const &s : svec){                          
  cout << s << " ";                              
 }                                       
 cout << endl;                                 
 //由于调换了shorter参数的位置，所以变成了降序                 
 sort(svec.begin(), svec.end(),bind(shorter, _2, _1));             
 for(auto const &s : svec){                          
  cout << s << " ";                              
 }                                       
 cout << endl;                                 
 */
 //bind引用,必须使用ref或者cref函数，把对象转化成引用，不能用&         
 ostream &os = cout;
 const char c = ' ';
 vector<string> svec{"aab","d","aa","bb","e","bbb"};
 for_each(svec.begin(),svec.end(),[&os, c](const string &s){
   os << s << c;
  });
 os << endl;
 for_each(svec.begin(),svec.end(),bind(print, ref(os), _1, cref(c)));
 os << endl;
 cout << c << endl;
}