Notes on proposal

[mbianco]

notes for the r3 branch

• Need some examples of use, like a note showing hot to instantiate and accessing an element of the array_erf?
• Have separate sessions for Properties, Mapping, and Layout (the layout is just a class with a subclass of type mapping. I think in the previous version this was a little hidden, but with the format of the standard, people should be able to follow. Maybe put the layout before the mapping. I don't know if people would be puzzled more by the forward definition or the delayed one.
• is_layout could be implemented as

#include <type_traits>                                                                                                                                                                                      

template <typename T...>                                                                                                                                                                                    
using void_t = void;                                                                                                                                                                                        

struct my_layout {                                                                                                                                                                                          
    template <typename DType, DType...>                                                                                                                                                                     
    struct mapping {                                                                                                                                                                                        
        using is_mapping = std::true_type;                                                                                                                                                                  
    };                                                                                                                                                                                                      

};                                                                                                                                                                                                          

template <typename T, typename Dummy=void>                                                                                                                                                                  
struct is_layout : std::false_type {};                                                                                                                                                                      

template <typename T>                                                                                                                                                                                       
struct is_layout<T, void_t<typename T::template mapping<int> > > : std::true_type {};                                                                                                                       

int main() {                                                                                                                                                                                                
    static_assert(is_layout<my_layout>::value, "");                                                                                                                                                         
    static_assert(!is_layout<int>::value, "");                                                                                                                                                              

}                                                                                                                                                                                                           

• The "standard layouts" section should be renamed, I think, into "provided layouts", or "standard provided layouts".
• Name "domain, codomains, mapping types" into "Types"?

[hcedwar]

done in current version