Map comparison : map compare « map multimap « C++ Tutorial

1. C++ Tutorial
2. map multimap
3. map compare

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <iomanip>
#include <map>
#include <string>
#include <algorithm>
using namespace std;

/* function object to compare strings
 * - allows you to set the comparison criterion at runtime
 * - allows you to compare case insensitive
 */
class RuntimeStringCmp {
  public:
    // constants for the comparison criterion
    enum cmp_mode {normal, nocase};
  private:
    // actual comparison mode
    const cmp_mode mode;

    // auxiliary function to compare case insensitive
    static bool nocase_compare (char c1, char c2)
    {
        return toupper(c1) < toupper(c2);
    }

  public:  
    // constructor: initializes the comparison criterion
    RuntimeStringCmp (cmp_mode m=normal) : mode(m) {
    }

    // the comparison
    bool operator() (const string& s1, const string& s2) const {
        if (mode == normal) {
            return s1<s2;
        }
        else {
            return lexicographical_compare (s1.begin(), s1.end(),
                                            s2.begin(), s2.end(),
                                            nocase_compare);
        }
    }
};

/* container type:
 * - map with
 *       - string keys
 *       - string values
 *       - the special comparison object type
 */
typedef map<string,string,RuntimeStringCmp> StringStringMap;

// function that fills and prints such containers
void fillAndPrint(StringStringMap& coll);

int main()
{
    // create a container with the default comparison criterion
    StringStringMap coll1;
    fillAndPrint(coll1);

    // create an object for case-insensitive comparisons
    RuntimeStringCmp ignorecase(RuntimeStringCmp::nocase);

    // create a container with the case-insensitive comparisons criterion
    StringStringMap coll2(ignorecase);
    fillAndPrint(coll2);
}

void fillAndPrint(StringStringMap& coll)
{
    // fill insert elements in random order
    coll["Deutschland"] = "Germany";
    coll["deutsch"] = "German";
    coll["Haken"] = "snag";
    coll["arbeiten"] = "work";
    coll["Hund"] = "dog";
    coll["gehen"] = "go";
    coll["Unternehmen"] = "enterprise";
    coll["unternehmen"] = "undertake";
    coll["gehen"] = "walk";
    coll["Bestatter"] = "undertaker";

    // print elements
    StringStringMap::iterator pos;
    cout.setf(ios::left, ios::adjustfield);
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        cout << setw(15) << pos->first.c_str() << " "
             << pos->second << endl;
    }
    cout << endl;
}

Bestatter       undertaker
Deutschland     Germany
Haken           snag
Hund            dog
Unternehmen     enterprise
arbeiten        work
deutsch         German
gehen           walk
unternehmen     undertake

arbeiten        work
Bestatter       undertaker
deutsch         German
Deutschland     Germany
gehen           walk
Haken           snag
Hund            dog
Unternehmen     undertake