added another example

[SVN r9177]

counting_iterator_example.cpp

@@ -6,7 +6,10 @@
 
 #include <boost/config.hpp>
 #include <iostream>
+#include <iterator>
+#include <vector>
 #include <boost/counting_iterator.hpp>
+#include <boost/iterator_adaptors.hpp>
 
 int main(int, char*[])
 {
@@ -17,12 +20,33 @@ int main(int, char*[])
   std::cout << std::endl;
 
   // Example of using make_counting_iterator()
-  std::cout << "counting from -5 to 5:" << std::endl;
+  std::cout << "counting from -5 to 4:" << std::endl;
   std::copy(boost::make_counting_iterator(-5),
 	    boost::make_counting_iterator(5),
 	    std::ostream_iterator<int>(std::cout, " "));
   std::cout << std::endl;
 
+  // Example of using counting iterator to create an array of pointers.
+  const int N = 7;
+  std::vector<int> numbers;
+  // Fill "numbers" array with [0,N)
+  std::copy(boost::make_counting_iterator(0), boost::make_counting_iterator(N),
+	    std::back_inserter(numbers));
+  std::vector<int*> pointers;
 
+  // Use counting iterator to fill in the array of pointers.
+  std::copy(boost::make_counting_iterator(numbers.begin()),
+	    boost::make_counting_iterator(numbers.end()),
+	    std::back_inserter(pointers));
+
+  // Use indirect iterator to print out numbers by accessing
+  // them through the array of pointers.
+  std::cout << "indirectly printing out the numbers from 0 to " 
+	    << N << std::endl;
+  std::copy(boost::make_indirect_iterator(pointers.begin()),
+	    boost::make_indirect_iterator(pointers.end()),
+	    std::ostream_iterator<int>(std::cout, " "));
+  std::cout << std::endl;
+  
   return 0;
 }