Rozental, Gennadiy wrote:

Here some question I've got while reading submitted library.

1. What is an advantage if using this library for scalar types (vs. defining operator<<)

Do you mean for things like int, Person, etc. If that is the case, the default behaviour of the library is to delegate output of these types to operator<<, so it doesn't do much. However, with support for a fmt::serialize formatter that calls 'serialize' instead of <<, you can register a particular class as being serializable so my type deduction system knows to associate instances of that type with fmt::serialize, so you can then do: // new design std::cout << io::object( my_serializable_object ) << '\n'; std::cout << io::object( vec_of_serializable_objects ) << '\n'; // [ ..., ..., ... ] The advantage of using this for things like std::complex or boost::math::quaternion that already supply << and >> operators is if you want to have control over how a type is rendered, e.g.: // new design std::cout << io::object( complex_val ).decorate( "", "", " + i" ) << " = " << io::object( complex_val ).decorate( "( ", " )" ) << '\n';

2. If primary target is collection formatting wouldn't it be better to name library "collection formats something"?

This is a good idea. The name is from when the library just had output support, thus the "outfmt" directory in the sandbox. I am thinking about moving to a "formatter" directory. What do other people think?

3. If there is a way to assign format to collection/type combination permanently (through global operator <<), why would I want to do it in every instance of output operation?

Do you mean: std::vector< int > vec; std::cout << "vector = " << vec << '\n'; // [1] std::cout << "vector = " << io::formatob( vec ) << '\n'; // [2] using [1] vs using [2]? If so, these are the same, but the second allows you to customize the decoration around the sequence, for example: std::cout << io::formatob( vec ).format( " : " ); // [ 1 : 2 : 3 : 4 ]

4. What is an advantage of using this library to assign format to collection/type combination permanently vs. explicit implementation (using FOREACH construct for example)

Using a foreach construct you would need to hand-code the surrounding decoration, e.g.: // output: { a + b + c } std::cout << "{ "; foreach( char ch : vec ) { std::cout << ch; if( !atend ) std::cout << " + "; } std::cout << " }"; vs: std::cout << io::formatob( vec ).format( "{ ", " }", " + " ); // output: { a + b + c } If you have a nested construct, such as int tictactoe[ 3 ][ 3 ], std::list< std::list< float > > or math::matrix4x4< float > then outputting/inputting it manually would be more complex, whereas my library has all the machinery to handle this simply.

5. Why do we need boost::io::range? Couldn't we use boost::range instead?

I suppose it would be possible to use boost::range::make_iterator_range instead. The only thing I have against this is its length. Consider: // new design using boost::range::make_iterator_range; namespace range = boost::range; namespace io = boost::io; std::cout << io::object( range::make_iterator_range( i, i + 7 )); // [1] std::cout << io::object( make_iterator_range( i, i + 7 )); // [2] std::cout << io::object( io::range( i, i + 7 )); // [3] If only you could alias functions, e.g.: namespace io{ alias range = boost::range::make_iterator_range; }

6. In a formatter usage how would I guess what is what? boost::io::formatter< char * > fmt( "\ ", " /", " | " ); boost::io::formatob( vec, boost::io::containerfmt()).format( fmt );

I have revised the names, so that is now: namespace fmt = boost::io::format; io::sequence_decorators< char > seq( "\\ ", " /", " | " ); io::object( vec, fmt::container()).decorate( seq );

7. Who come format calls order dependent? boost::io::formatob( vec, boost::io::containerfmt()).format( fmt ).format( " : " );

format( fmt ) is called first, then format( " : " ). Thus, you will have "\ a : b : c /" as the formatting.

8. If I got vector<vector<int> >. How do I supply separators for both internal and external vectors?

You apply the 'format' function to containerfmt(). For example: boost::io::formatob( vec, containerfmt( containerfmt().format( " : " )).format( " + " )); // output: [ [ a : b : c ] + [ x : y : z ] + ... ]

9. Let say I print vector<char>. Is there way to print it like this: { 'a', 'b', '0x01', ' ' }

Yes. You need to provide a wrappedfmt() format object. For example: formatob( vec, containerfmt( wrappedfmt().format( "'", "'" ))).format( "{ ", " }" ); // output: { 'a', 'b', 'c' } With the 0x01 character, special treatment needs to be applied. You will need to supply a custom format object to see if the character is printable, e.g.: class char_escape { public: typedef void traits_type; typedef const char * format_type; typedef boost::io::seq_type< -1 > formatter_type; public: template< typename CharT, typename TraitsT > static std::basic_ostream< CharT, TraitsT > & write( std::basic_ostream< CharT, TraitsT > & os, CharT value ) const { if( isprintable( value )) return( os << value ); return( os << "0x" << int( value )); } }; formatob( vec, containerfmt( wrappedfmt( char_escape()).format( "'", "'" ))).format( "{ ", " }" ); // output: { 'a', 'b', 'c' } Regards, Reece _________________________________________________________________ Use MSN Messenger to send music and pics to your friends http://www.msn.co.uk/messenger