Le samedi 05 décembre 2015 à 12:08 +0000, Bubke Marco a écrit :
> >
> >> - template code (esp., but not necessarily only, when the type name
> >> would require the use of 'typename')
> >
> > This is the one i’m not at ease with. Template code tends to be
> > difficult to read, partly *because* there’s no type information. For
> > readability concerns, i would prefer a local typedef named by the
> > concept. Yes, that makes it two lines instead of one, but i think that’s
> > one case where hinting the reader with a well-chosen type name makes a
> > lot of sense.
>
> Most typedefs I have seen was about hiding pointer or container types like
> CursorPointer or Cursors. But is CursorPointer a unique pointer, a shared
> pointer and which flavor is it. Cursors is the same because it could be
> std::vector or QList. Some would hide a dictionary behind this name. So the
> typedef can be misleading. In that case I prefer auto.
>
> std::shared<Cursor> cursorPointer = document.cursorAtPostion(46);
>
> CursorPointer cursorPointer = document.cursorAtPostion(46);
>
> auto cursorPointer = document.cursorAtPostion(46);
>
> I prefer the last but we need good tooling to show the type. It would be nice
> to have much more information like size, is it movable or copyable. It is
> not only the type and we can provide that information.
My understanding of Marc’s proposal was that it was more for the
following case :
template<typename List> void algorithm(List& input)
{
typename List::value_type& first = input.front();
...
}
replaced by :
template<typename List> void algorithm(List& input)
{
auto& first = input.front();
...
}
whereas i prefer
template<typename List> void algorithm(List& input)
{
typedef typename List::value_type Serializable;
// there are some requirements on List : item_type must be
// Serializable : now i can look the doc to see what a
// Serializable is
Serializable& first = input.front();
// i know what to expect from first, which methods i can call
...
}
I think the latter improves readability over the two others, because it
just gives more information to the reader. And this information is
currently *not* given by the type system, because concepts do not exists
in the type system yet. No tooling will ever give you a type information
here : it depends on the template instanciation.
Regards,
Julien Blanc
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