Multimap (STL) equal_range function

[AkashAg]

Hi, I have a doubt regarding multimap::equal_range function for the following program.

int main ()
{
multimap<char,int> mymm;
multimap<char,int>::iterator it,it1,it2;
pair<multimap<char,int>::iterator,multimap<char,int>::iterator> ret;

mymm.insert(std::pair<const char,int>('a',10));
mymm.insert(std::pair<const char,int>('b',20));
mymm.insert(std::pair<const char,int>('b',30));
mymm.insert(std::pair<const char,int>('c',40));
mymm.insert(std::pair<const char,int>('b',50));
mymm.insert(std::pair<const char,int>('c',60));
mymm.insert(std::pair<const char,int>('d',70));

cout << "mymm contains:\n";
for (char ch='a'; ch<='d'; ch++)
{
cout << ch << " =>";
ret = mymm.equal_range(ch);
it1 = ret.first;
it2 = ret.second;
cout << (*it1).second << " " << (*it2).second << endl;
for (it=ret.first; it!=ret.second; ++it)
cout << " " << (*it).second;
cout << endl;
}

return 0;
}

It is giving following output:

mymm contains:
a =>10 20
10
b =>20 40
20 30 50
c =>40 70
40 60
d =>70 70

What I am not getting is the o/p for 'b'. I think it should be

b =>20 60
20 30 50

Please revert. BR, Akash

[CPallini]

The output is correct, the map is orderd by the key. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[Stephen Hewitt]

Some suggestions:

• Use typedefs:

  typedef multimap<char,int> char2int;
  typedef char2int::iterator char2map_it;
  char2map mymm;
  char2map_it it,it1,it2;
  pair<char2map_it, char2map_it> ret;

  There's no need to repeat long type names all over the place. One design decision should, if possible, be expressed in one place (or as few as possible): Now I can change from a map from chars to ints to a map from chars to std::strings by changing one line, for example.

• Use make_pair from #include <utility>:

  mymm.insert(make_pair('a', 10));

None of this is related to your question...

Steve