Thread: iterator missunderstanding.

Here is some code I half stole from the c++ referance website and filled in a little for my purposes. Initially I wanted to make sure I understood the equal_range function:

this is my understanding of the code below.

calling equal_range returns something that looks like : <<'b',20>, <c,30>>
it becomes <'b',20>
when it gets to the loop, it gets set to <'b',20> again
calling erase should remove the "b" key and its value from the map.
and my output should look like

a->10
b->0
c->30
d->40
e->50
f->60

unfortunately it looks like this:
a->10
b->0
c->30
d->0
e->0
f->0

in fact, a,c and e work as expected, removing the equal_range parameter.
the rest have odd functionality. F erases the whole map, which sorta makes sense to me, but b, and d have me stumped.

any thoughts on this? Also, I know this is not the best way to accomplish this, I wrote this to help better understand a much larger project.

Thanks!

Code:

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

int main ()
{
  map<char,int> * mymap = new map<char,int>();
  map<char,int>::iterator it;
  pair<map<char,int>::iterator,map<char,int>::iterator> ret;
  bool yes = true;
  // insert some values:
  	(*mymap)['a']=10;
  	(*mymap)['b']=20;
  	(*mymap)['c']=30;
  	(*mymap)['d']=40;
  	(*mymap)['e']=50;
  	(*mymap)['f']=60;
  
	ret = mymap->equal_range('b');
	it = ret.first;
	if(it != mymap->end()){
		cout << "lower bound points to: ";
	  	cout << ret.first->first << " => " << ret.first->second << endl;
  		
		cout << "upper bound points to: ";
  		cout << ret.second->first << " => " << ret.second->second << endl;

		for(it=ret.first; it!=ret.second; ++it){
			if(yes){
				mymap->erase(it);
				cout << "erased the iter:"<< it->first << endl;
			}	
		}
		for(int i = 'a'; i<='f'; i++){
			cout << char(i) << "->" << (*mymap)[i] << endl;
		}

	}
	return 0;
}