C++ Notes: STL Containers - pair utility class

The pair template class is defined in <utility> to keep pairs of values. Aside from some functions that return two values in a pair, the elements of a map are stored as key-value pairs. The following illustrates the declaration and use of pair, with it's two public fields, first and second.

Example

  1 
  2 
  3 
  4 
  5 
  6 
  7 
  8 
  9 
 10 
 11 
 12 
 13 
 14 
 15 
 16 
 17 
 18 
 19 
 20 
 21 
 22 
 23 
 24 
 25 
 26 
 27 
 28 
 29 
 30 
 31 
 32 
 33 
 34 
 35 
 36 
 37 
 38 
 39 
 40 

// map/pair-test.cpp - Show basic use of pair.
// 2004-02-29 - Fred Swartz - Rodenbach

#include <utility>
#include <iostream>
#include <string>
#include <map>
using namespace std;

int main() {
    //-- Declare a pair variable.
    pair<string, int> pr1;
    
    //-- Declare and initialize with constructor.
    pair<string, int> pr2("heaven", 7);
    cout << pr2.first << "=" << pr2.second << endl;
    // Prints heaven=7
    
    //-- Declare and initialize pair pointer.
    pair<string, int>* prp = new pair<string, int>("yards", 9);
    cout << prp->first << "=" << prp->second << endl;
    // Prints yards=9
    
    //-- Declare map and assign value to keys.
    map<string, string> engGerDict;
    engGerDict["shoe"] = "Schuh";
    engGerDict["head"] = "Kopf";
    
    //-- Iterate over map.  Iterator value is a key-value pair.
    //   Iteration in map is in sorted order.
    map<string, string>::const_iterator it;
    for (it=engGerDict.begin(); it != engGerDict.end(); ++it) {
        cout << it->first << "=" << it->second << endl;
    }
    // Prints head=kopf
    //        shoe=Schuh
    
    system("PAUSE");
    return 0;
}