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    copied!<p>This solution was inspired by Marcelo's solution, with a few changes:</p> <pre><code>#include &lt;iostream&gt; #include &lt;iterator&gt; #include &lt;type_traits&gt; #include &lt;vector&gt; #include &lt;algorithm&gt; // This works similar to ostream_iterator, but doesn't print a delimiter after the final item template&lt;typename T, typename TChar = char, typename TCharTraits = std::char_traits&lt;TChar&gt; &gt; class pretty_ostream_iterator : public std::iterator&lt;std::output_iterator_tag, void, void, void, void&gt; { public: typedef TChar char_type; typedef TCharTraits traits_type; typedef std::basic_ostream&lt;TChar, TCharTraits&gt; ostream_type; pretty_ostream_iterator(ostream_type &amp;stream, const char_type *delim = NULL) : _stream(&amp;stream), _delim(delim), _insertDelim(false) { } pretty_ostream_iterator&lt;T, TChar, TCharTraits&gt;&amp; operator=(const T &amp;value) { if( _delim != NULL ) { // Don't insert a delimiter if this is the first time the function is called if( _insertDelim ) (*_stream) &lt;&lt; _delim; else _insertDelim = true; } (*_stream) &lt;&lt; value; return *this; } pretty_ostream_iterator&lt;T, TChar, TCharTraits&gt;&amp; operator*() { return *this; } pretty_ostream_iterator&lt;T, TChar, TCharTraits&gt;&amp; operator++() { return *this; } pretty_ostream_iterator&lt;T, TChar, TCharTraits&gt;&amp; operator++(int) { return *this; } private: ostream_type *_stream; const char_type *_delim; bool _insertDelim; }; #if _MSC_VER &gt;= 1400 // Declare pretty_ostream_iterator as checked template&lt;typename T, typename TChar, typename TCharTraits&gt; struct std::_Is_checked_helper&lt;pretty_ostream_iterator&lt;T, TChar, TCharTraits&gt; &gt; : public std::tr1::true_type { }; #endif // _MSC_VER &gt;= 1400 namespace std { // Pre-declarations of container types so we don't actually have to include the relevant headers if not needed, speeding up compilation time. // These aren't necessary if you do actually include the headers. template&lt;typename T, typename TAllocator&gt; class vector; template&lt;typename T, typename TAllocator&gt; class list; template&lt;typename T, typename TTraits, typename TAllocator&gt; class set; template&lt;typename TKey, typename TValue, typename TTraits, typename TAllocator&gt; class map; } // Basic is_container template; specialize to derive from std::true_type for all desired container types template&lt;typename T&gt; struct is_container : public std::false_type { }; // Mark vector as a container template&lt;typename T, typename TAllocator&gt; struct is_container&lt;std::vector&lt;T, TAllocator&gt; &gt; : public std::true_type { }; // Mark list as a container template&lt;typename T, typename TAllocator&gt; struct is_container&lt;std::list&lt;T, TAllocator&gt; &gt; : public std::true_type { }; // Mark set as a container template&lt;typename T, typename TTraits, typename TAllocator&gt; struct is_container&lt;std::set&lt;T, TTraits, TAllocator&gt; &gt; : public std::true_type { }; // Mark map as a container template&lt;typename TKey, typename TValue, typename TTraits, typename TAllocator&gt; struct is_container&lt;std::map&lt;TKey, TValue, TTraits, TAllocator&gt; &gt; : public std::true_type { }; // Holds the delimiter values for a specific character type template&lt;typename TChar&gt; struct delimiters_values { typedef TChar char_type; const TChar *prefix; const TChar *delimiter; const TChar *postfix; }; // Defines the delimiter values for a specific container and character type template&lt;typename T, typename TChar&gt; struct delimiters { static const delimiters_values&lt;TChar&gt; values; }; // Default delimiters template&lt;typename T&gt; struct delimiters&lt;T, char&gt; { static const delimiters_values&lt;char&gt; values; }; template&lt;typename T&gt; const delimiters_values&lt;char&gt; delimiters&lt;T, char&gt;::values = { "{ ", ", ", " }" }; template&lt;typename T&gt; struct delimiters&lt;T, wchar_t&gt; { static const delimiters_values&lt;wchar_t&gt; values; }; template&lt;typename T&gt; const delimiters_values&lt;wchar_t&gt; delimiters&lt;T, wchar_t&gt;::values = { L"{ ", L", ", L" }" }; // Delimiters for set template&lt;typename T, typename TTraits, typename TAllocator&gt; struct delimiters&lt;std::set&lt;T, TTraits, TAllocator&gt;, char&gt; { static const delimiters_values&lt;char&gt; values; }; template&lt;typename T, typename TTraits, typename TAllocator&gt; const delimiters_values&lt;char&gt; delimiters&lt;std::set&lt;T, TTraits, TAllocator&gt;, char&gt;::values = { "[ ", ", ", " ]" }; template&lt;typename T, typename TTraits, typename TAllocator&gt; struct delimiters&lt;std::set&lt;T, TTraits, TAllocator&gt;, wchar_t&gt; { static const delimiters_values&lt;wchar_t&gt; values; }; template&lt;typename T, typename TTraits, typename TAllocator&gt; const delimiters_values&lt;wchar_t&gt; delimiters&lt;std::set&lt;T, TTraits, TAllocator&gt;, wchar_t&gt;::values = { L"[ ", L", ", L" ]" }; // Delimiters for pair template&lt;typename T1, typename T2&gt; struct delimiters&lt;std::pair&lt;T1, T2&gt;, char&gt; { static const delimiters_values&lt;char&gt; values; }; template&lt;typename T1, typename T2&gt; const delimiters_values&lt;char&gt; delimiters&lt;std::pair&lt;T1, T2&gt;, char&gt;::values = { "(", ", ", ")" }; template&lt;typename T1, typename T2&gt; struct delimiters&lt;std::pair&lt;T1, T2&gt;, wchar_t&gt; { static const delimiters_values&lt;wchar_t&gt; values; }; template&lt;typename T1, typename T2&gt; const delimiters_values&lt;wchar_t&gt; delimiters&lt;std::pair&lt;T1, T2&gt;, wchar_t&gt;::values = { L"(", L", ", L")" }; // Functor to print containers. You can use this directly if you want to specificy a non-default delimiters type. template&lt;typename T, typename TChar = char, typename TCharTraits = std::char_traits&lt;TChar&gt;, typename TDelimiters = delimiters&lt;T, TChar&gt; &gt; struct print_container_helper { typedef TChar char_type; typedef TDelimiters delimiters_type; typedef std::basic_ostream&lt;TChar, TCharTraits&gt;&amp; ostream_type; print_container_helper(const T &amp;container) : _container(&amp;container) { } void operator()(ostream_type &amp;stream) const { if( delimiters_type::values.prefix != NULL ) stream &lt;&lt; delimiters_type::values.prefix; std::copy(_container-&gt;begin(), _container-&gt;end(), pretty_ostream_iterator&lt;typename T::value_type, TChar, TCharTraits&gt;(stream, delimiters_type::values.delimiter)); if( delimiters_type::values.postfix != NULL ) stream &lt;&lt; delimiters_type::values.postfix; } private: const T *_container; }; // Prints a print_container_helper to the specified stream. template&lt;typename T, typename TChar, typename TCharTraits, typename TDelimiters&gt; std::basic_ostream&lt;TChar, TCharTraits&gt;&amp; operator&lt;&lt;(std::basic_ostream&lt;TChar, TCharTraits&gt; &amp;stream, const print_container_helper&lt;T, TChar, TDelimiters&gt; &amp;helper) { helper(stream); return stream; } // Prints a container to the stream using default delimiters template&lt;typename T, typename TChar, typename TCharTraits&gt; typename std::enable_if&lt;is_container&lt;T&gt;::value, std::basic_ostream&lt;TChar, TCharTraits&gt;&amp;&gt;::type operator&lt;&lt;(std::basic_ostream&lt;TChar, TCharTraits&gt; &amp;stream, const T &amp;container) { stream &lt;&lt; print_container_helper&lt;T, TChar, TCharTraits&gt;(container); return stream; } // Prints a pair to the stream using delimiters from delimiters&lt;std::pair&lt;T1, T2&gt;&gt;. template&lt;typename T1, typename T2, typename TChar, typename TCharTraits&gt; std::basic_ostream&lt;TChar, TCharTraits&gt;&amp; operator&lt;&lt;(std::basic_ostream&lt;TChar, TCharTraits&gt; &amp;stream, const std::pair&lt;T1, T2&gt; &amp;value) { if( delimiters&lt;std::pair&lt;T1, T2&gt;, TChar&gt;::values.prefix != NULL ) stream &lt;&lt; delimiters&lt;std::pair&lt;T1, T2&gt;, TChar&gt;::values.prefix; stream &lt;&lt; value.first; if( delimiters&lt;std::pair&lt;T1, T2&gt;, TChar&gt;::values.delimiter != NULL ) stream &lt;&lt; delimiters&lt;std::pair&lt;T1, T2&gt;, TChar&gt;::values.delimiter; stream &lt;&lt; value.second; if( delimiters&lt;std::pair&lt;T1, T2&gt;, TChar&gt;::values.postfix != NULL ) stream &lt;&lt; delimiters&lt;std::pair&lt;T1, T2&gt;, TChar&gt;::values.postfix; return stream; } // Used by the sample below to generate some values struct fibonacci { fibonacci() : f1(0), f2(1) { } int operator()() { int r = f1 + f2; f1 = f2; f2 = r; return f1; } private: int f1; int f2; }; int main() { std::vector&lt;int&gt; v; std::generate_n(std::back_inserter(v), 10, fibonacci()); std::cout &lt;&lt; v &lt;&lt; std::endl; // Example of using pretty_ostream_iterator directly std::generate_n(pretty_ostream_iterator&lt;int&gt;(std::cout, ";"), 20, fibonacci()); std::cout &lt;&lt; std::endl; } </code></pre> <p>Like Marcelo's version, it uses an is_container type trait that must be specialized for all containers that are to be supported. It may be possible to use a trait to check for <code>value_type</code>, <code>const_iterator</code>, <code>begin()</code>/<code>end()</code>, but I'm not sure I'd recommend that since it might match things that match those criteria but aren't actually containers, like <code>std::basic_string</code>. Also like Marcelo's version, it uses templates that can be specialized to specify the delimiters to use.</p> <p>The major difference is that I've built my version around a <code>pretty_ostream_iterator</code>, which works similar to the <code>std::ostream_iterator</code> but doesn't print a delimiter after the last item. Formatting the containers is done by the <code>print_container_helper</code>, which can be used directly to print containers without an is_container trait, or to specify a different delimiters type.</p> <p>I've also defined is_container and delimiters so it will work for containers with non-standard predicates or allocators, and for both char and wchar_t. The operator&lt;&lt; function itself is also defined to work with both char and wchar_t streams.</p> <p>Finally, I've used <code>std::enable_if</code>, which is available as part of C++0x, and works in Visual C++ 2010 and g++ 4.3 (needs the -std=c++0x flag) and later. This way there is no dependency on Boost.</p>
 

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