C++ Cookbook

7.11. Printing a Range to a Stream

Problem

You have a range of elements that you want to print to a stream, most likely cout for debugging.

Solution

Write a function template that takes a range or a container, iterates through each element, and uses the copy algorithm and an ostream_iterator to write each element to a stream. If you want more control over formatting, write your own simple algorithm that iterates through a range and prints each element to the stream. (See Example 7-11.)

Example 7-11. Printing a range to a stream

#include <iostream>
#include <string>
#include <algorithm>
#include <iterator>
#include <vector>

using namespace std;

int main() {

   // An input iterator is the opposite of an output iterator: it
   // reads elements from a stream as if it were a container.
   cout << "Enter a series of strings: ";
   istream_iterator<string> start(cin);
   istream_iterator<string> end;
   vector<string> v(start, end);

   // Treat the output stream as a container by using an
   // output_iterator.  It constructs an output iterator where writing
   // to each element is equivalent to writing it to the stream.
   copy(v.begin(), v.end(), ostream_iterator<string>(cout, ", "));
}

The output for Example 7-11 might look like this:

Enter a series of strings: z x y a b c
^Z
z, x, y, a, b, c,

Discussion

A stream iterator is an iterator that is based on a stream instead of a range of elements in some container, and stream iterators allow you to treat stream input as an input iterator (read from the dereferenced value ...