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.
All Platforms
Remarks
An STL collection is also known as a container. For more information, see STL Containers.
Examples
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
Windows Runtime
Remarks
There are no platform-specific remarks about this feature.
Requirements
Compiler option: /ZW
Common Language Runtime
Remarks
There are no platform-specific remarks about this feature.
Requirements
Compiler option: /clr