Re: cout formatting + copy algorithm

"Daniel T." <>
Sat, 25 Sep 2010 00:28:30 -0400
suresh <> wrote:

I display a vector using copy algorithm like this.

copy(v.begin(),v.end(),ostream_iterator<int>(cout," ");

suppose i want to set the width or the fill character, what can i do?
Of course I can use a for loop instead of copy algorithm but my
question is, while using copy algorithm, is it possible to format

You can do it, but is it worth it?

template < typename T, typename Elem = char, typename Tr =
char_traits<Elem> >
struct OStreamIteratorWidth : iterator<output_iterator_tag, void, void,
void, void> {
   typedef Elem char_type;
   typedef Tr traits_type;
   typedef basic_ostream<Elem, Tr> ostream_type;
   OStreamIteratorWidth(ostream_type& o) : os(o), wi(0) { }
   OStreamIteratorWidth(ostream_type& o, int w): os(o), wi(w) { }
   OStreamIteratorWidth& operator*() { return *this; }
   OStreamIteratorWidth& operator++() { return *this; }
   OStreamIteratorWidth operator++(int) { return *this; }
   OStreamIteratorWidth& operator=(const T& t) {
      os << setw(wi) << t;
      return *this;
   ostream_type& os;
   int wi;

void fn(vector<int>& v) {
   copy(v.begin(), v.end(), OStreamIteratorWidth<int>(cout, 5));

using for_each is moderately easier:

template < typename T >
struct OutputWithWidth : unary_function<T, void>
   ostream& os;
   int width;
   OutputWithWidth(ostream& o, int w): os(o), width(w) { }
   void operator()(const T& t) {
      os << setw(width) << t;

void fn(vector<int>& v) {
   for_each(v.begin(), v.end(), OutputWithWidth<int>(cout, 5));

which points to a straight loop:

void fn(vector<int>& v) {
   for (vector<int>::const_iterator it = v.begin(); it != v.end(); ++it)
      cout << setw(5) << *it;

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