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#include 
   
    #include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         using namespace std;int main(){//first you read contents from a outside filevector
         
           vec;ifstream in("file.txt");if(!in) cout << "failure" << endl;//else cout << "success " << endl; istream_iterator
          
            iter(in),eof;while(iter != eof) vec.push_back(*iter ++);for(auto i : vec) cout << i << " ";cout << endl;//second you will read a file from outsideofstream of("output.txt");ofstream of1("output2.txt");ostream_iterator
           
             out(of,"a elem\n");ostream_iterator
            
              out1(of1);for(auto i : vec) out = i;//copy(vec.begin(),vec.end(),out1);ifstream inn("output.txt");if(!inn) cout << "open a file failure." << endl;istream_iterator
             
               iter1(inn),eoff;copy(iter,eoff,out1);//为何out1不能完成工作??? return 0;}
             
            
           
          
         
        
       
      
     
    
   

#include 
   
    #include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          #include 
          
           using namespace std;int main(){ifstream in("file.txt");istream_iterator
           
             iter(in),eof;vector
            
              vint;//下一行的错误在于accumulate的第一个参数应该是istream_iterator类型，但是这里给了一个//ifstream类型，我们这里应用的是流iterator，但是没有文件iterator这一说....//这个错误真是太隐蔽了int result = accumulate(in,eof,vint.begin());//为何提示没有匹配的函数?因为这里cout << result << endl; return 0;}