Re: Explanation for behavior

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Mon, 16 Jul 2007 14:10:10 -0400

Message-ID:

<f7gca1$t2v$1@news.datemas.de>

rogerhillster@gmail.com wrote:

I have the below code for printing out the contents of a map.

Beyond the use of non-standard 'itoa', the code is OK (not perfect,
but OK).

The output prints the strings contained in the value for each key in
the map.

Yes.

In the first for loop, I am clearing the list contents and I am
storing the reference to the list in each of the map's entries.

No, you're not storing the reference. The 'map' stores a copy of the
list.

Could somebody let me know as to why even after clearing the contents
of the list, I can see different strings contained in the map for each
key?

Because the map contains copies of the list. Every time you assign
your list to 'tmap[i]', the list is _copied_ into the one contained
within the map.

Thanks,
Roger.

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

int main() {
typedef list<string> tslist;
tslist slist;
map<int, tslist> tmap;
int i = 0, j =0;
for (; i < 10; i++) {
slist.clear();
char str[10];
itoa(i, str, 10);
slist.push_front(string(str));
tmap[i] = slist;
}

i = 0;
for (; i < 10; i++) {
tslist temp = tmap[i];
tslist::iterator iter = temp.begin();
while(iter!=temp.end()) {
string& temp = *iter;
cout << temp.c_str() << endl;
iter++;
}
}
return 0;
}

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