How to deal with last comma, when making comma separated string? [duplicate]

Question

Possible Duplicates:
Don't print space after last number
Printing lists with commas C++

#include <vector> #include <iostream> #include <sstream> #include <boost/foreach.hpp> using namespace std;  int main() {    vector<int> VecInts;     VecInts.push_back(1);    VecInts.push_back(2);    VecInts.push_back(3);    VecInts.push_back(4);    VecInts.push_back(5);     stringstream ss;    BOOST_FOREACH(int i, VecInts)    {       ss << i << ",";    }     cout << ss.str();     return 0; } 

This prints out: 1,2,3,4,5, However I want: 1,2,3,4,5

How can I achieve that in an elegant way?

I see there is some confusion about what I mean with "elegant": E.g. no slowing down "if-clause" in my loop. Imagine 100.000 entries in the vector! If that is all you have to offer, I'd rather remove the last comma after I have gone through the loop.

Answer 1

How about this:

#include <iostream> #include <vector> #include <algorithm> #include <iterator> #include <string> #include <sstream>  int main() {    std::vector<int> v;     v.push_back(1);    v.push_back(2);    v.push_back(3);    v.push_back(4);    v.push_back(5);     std::ostringstream ss;    if(!v.empty()) {       std::copy(v.begin(), std::prev(v.end()), std::ostream_iterator<int>(ss, ", "));       ss << v.back();    }    std::cout << ss.str() << "\n"; } 

No need to add extra variables and doesn't even depend on boost! Actually, in addition to the "no additional variable in the loop" requirement, one could say that there is not even a loop :)

Answer 2

Detecting the one before last is always tricky, detecting the first is very easy.

bool first = true; stringstream ss; BOOST_FOREACH(int i, VecInts) {   if (!first) { ss << ","; }   first = false;   ss << i; }