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Printing the contents of STL containers in a generic way

Written by

Andy

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A generic Print function

A way of using STL algorithms combined with template functions as a means of printing the contents of any type of STL container (eg a std::vector), containing any generic data type (eg int, std::string etc). typename T defines the generic data type held by the container, while typename InputIterator describes the STL container iterators passed to it:

template<typename T, typename InputIterator>
void Print(std::ostream& ostr, 
	       InputIterator itbegin, 
		   InputIterator itend, 
		   const std::string& delimiter)
{
	std::copy(itbegin, 
		  itend, 
		  std::ostream_iterator<T>(ostr, delimiter.c_str()));
}

Example 1: std::set containing std::strings

This following example shows how the generic Print function can output a std::set containing std::string data types:

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

typedef std::set<std::string>::iterator iter_s;

template<typename T, typename InputIterator>
void Print(std::ostream& ostr, 
	       InputIterator itbegin, 
	       InputIterator itend, 
	       const std::string& delimiter)
{
	std::copy(itbegin, 
		  itend, 
		  std::ostream_iterator<T>(ostr, delimiter.c_str()));
}

int main()
{
	std::string str[] = { "The", "cat", "in", "the", "hat" };
	std::set<std::string> s( str, str + sizeof( str ) / sizeof( str[ 0 ] ) );
	Print<std::string, iter_s>( std::cout, s.begin(), s.end(), "\n" );

	return 0;
}

Giving the following tokenized string output, delimited by newline characters, though not necessarily in the order they were inserted!

The
cat
hat
in
the

Example 2: std::vector containing ints

The following example shows how the same generic Print function can be used to output a std::vector containing int data types:

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

typedef std::vector<int>::iterator iter;

template<typename T, typename InputIterator>
void Print(std::ostream& ostr, 
	       InputIterator itbegin, 
	       InputIterator itend, 
	       const std::string& delimiter)
{
	std::copy(itbegin, itend, 
            std::ostream_iterator<T>(ostr, delimiter.c_str()));
}

int main()
{
	int vals[] = { 1, 2, 3, 4 };	
	std::vector<int> v( vals, vals + sizeof( vals ) / sizeof( vals[ 0 ] ) );

    Print<int, iter>( std::cout, v.begin(), v.end(), " " );	

	return 0;
}

Which print the set of integers stored in the std::vector, separated by whitespaces:

1 2 3 4

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