Iterating Over STL Collection By Using for each

 

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The for each keyword can be used to iterate over a Standard C++ Library (STL) collection.

Remarks

An STL collection is also known as a container. For more information, see STL Containers.

Example

The following code example uses for each to iterate over a <map>.

// for_each_stl.cpp  
// compile with: /EHsc  
#include <map>  
#include <iostream>  
#include <string>  
using namespace std;  
  
int main() {  
   int retval  = 0;  
   map<string, int> months;  
  
   months["january"] = 31;  
   months["february"] = 28;  
   months["march"] = 31;  
   months["april"] = 30;  
   months["may"] = 31;  
   months["june"] = 30;  
   months["july"] = 31;  
   months["august"] = 31;  
   months["september"] = 30;  
   months["october"] = 31;  
   months["november"] = 30;  
   months["december"] = 31;  
  
   map<string, int> months_30;  
  
   for each( pair<string, int> c in months )  
      if ( c.second == 30 )  
         months_30[c.first] = c.second;  
  
   for each( pair<string, int> c in months_30 )  
      retval++;  
  
   cout << "Months with 30 days = " << retval << endl;  
}  

Output

Months with 30 days = 4  

Example

The following code example uses a const reference (const&) for an iteration variable with STL containers. You can use a reference (&) as an iteration variable on any collection of a type that can be declared as a T&.

// for_each_stl_2.cpp  
// compile with: /EHsc  
#include <vector>  
#include <iostream>  
using namespace std;  
  
int main() {  
   int retval = 0;  
  
   vector<int> col(3);  
   col[0] = 10;  
   col[1] = 20;  
   col[2] = 30;  
  
   for each( const int& c in col )  
      retval += c;  
  
   cout << "retval: " << retval << endl;  
}  

Output

retval: 60  

Remarks

There are no platform-specific remarks about this feature.

Requirements

Compiler option: /ZW

Remarks

There are no platform-specific remarks about this feature.

Requirements

Compiler option: /clr

for each, in
Component Extensions for Runtime Platforms

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