From: John Torjo (john.lists_at_[hidden])
Date: 2004-09-22 02:08:36
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'; // [ ...,
>>..., ... ]
>
>
> I don't really interested in another serialization library. We already have
> one.
>
>
>>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';
>
>
>
> And you believe that I will keep repeating this code every time I need to
> print my complex value?
>
>
>
>>>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 ]
>
>
> No my question was Is there a way to assign custom (meaning different from
> one you selected) decoration permanently.
>
>
>>>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.
>
>
> Yeah. But I do it only once. And using foreach is way more flexible. I don't
> believe your library bring any advantage in this scenario.
>
>
>>>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; }
>
>
> IMO you shouldn't introduce yet another range notion.
>
> > >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 );
>
>
>
> IMO it's really bad idea to introduce interfaces that change meaning depend
> on number of arguments of the same type. Moreover it easy to confuse one
> with another.
>
> Your interface:
> ( str1, str2, str3 ) - open, close, separator
> ( str1, str2 ) - open, close
> ( str1 ) - separator
>
> Now If I do not use your library on everyday basis, And look on invocation
> of first function - how would I now what is what.
>
Yup - I definitely tend to agree with you here (see the
"outputformatters - using just one decorator string").
Best,
John
--
John Torjo
-- john_at_[hidden]
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