On Sun, Jul 22, 2012 at 11:18 AM, Markus Werle <numerical.simulation@web.de> wrote:
Fabio Fracassi wrote:
Just spelling out some thoughts I had while reading the docu:
Even though, it would help to have this information in the docu. The way it is written now feels a bit like playing Jeopardy, you present solutions and the reader tries to figure out the problem.
I would like to add to this: I got the impression that TypeErasure is something really great to have - if and only if you really understand the problem it solves and how to solve it.
Here I am in the same situation as with proto: I will read the docs again and again and not really get sure about whether I am doing it right.
This is not the first boost library that misses a great tutorial. I think we have a dilemma here: The C++ skill level of the library authors is (and has to be) so extraordinary that they fully understand the implementation of mpl or proto and that they simply do not understand that mediocre programmers as me (sorry for "only" 15 years of C++ experience) stumble over questions on a much lower level.
I enjoyed this and other threads and some comments in the docs that simply tell me I am an absolute beginner. For me reference docs are helpful when I am through the normal docs, not as a first contact.
Please note that I hesitate to blame Steven for the fact that the docs do not meet my needs. I expect TypeErasure to be a great library with a near- perfect and well-thought implementation, only the missing step-by-step intro is exactly my problem with this library. I can imagine that writing it should not be Steven's burden. Like for the STL which was not written by
IMO, users can/should fully expect the library authors to put as much effort in the documentation as in the library design and implementation.
Scott Meyers, but only perfectly explained.
@Steven:
If you have some more examples at hand, please insert them into the examples section.
If you have some silly little example of the problem the library solves, please put it into the introduction chapter. People might read the library description and not get a clue what it was meant for.
I suggested something like the example below to be added to the Introduction section: http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/... #include <boost/type_erasure/any.hpp> #include <boost/type_erasure/builtin.hpp> #include <boost/type_erasure/operators.hpp> #include <boost/mpl/vector.hpp> #include <iostream> struct display { public: template< typename T > explicit display ( T const& obj ) : obj_(obj) {} public: void print ( void ) { std::cout << obj_ << std::endl; } public: boost::type_erasure::any< boost::mpl::vector< boost::type_erasure::copy_constructible<> , boost::type_erasure::ostreamable<> > > obj_; }; int main ( void ) { display i(-1), d('x'); i.print(); d.print(); return 0; } I had to do something like this in the past where: 1. I didn't want display to be a template but I wanted it to handle generic types as passed to the constructor. 2. I knew a-priori the operations that display needed from T (e.g., operator<<). 3. I had to store the object of the generic type T so the operation on T could be performed later (e.g., by print). And Steven commented: On Tue, Jun 19, 2012 at 12:12 AM, Steven Watanabe <watanabesj@gmail.com> wrote:
This is a textbook use case for the library. Use TypeErasure states the intent of the code clearly. obj_ can hold any type that is CopyConstructible, and Ostreamable.
Right after this example, the Introduction section could note how Boost.TypeErasure generalize of Boost.Any, Boost.Function, and Boost.AnyIterator thus applying to the problem domain of these existing libraries in a more general sense -- respectively: any<mpl::vector<copy_constructible<>, typeid_<> > > // any any<mpl::vector<copy_constructible<>, typeid_<>, callable<void(int)> >
// function any<mpl::vector<forward_iterator<>, same_type<forward_iterator<>::value_type, int> > > // any iterator
All of this (example included) might be a good addition to the Introduction section. HTH, --Lorenzo