This commit aims to make Span implementation more in line with what is present in N4762:
- use appropiate index types where applicable.
- use typedefed type inside the class (index_type, reference, pointer, element_type)
- assertion where applicable
- restrict default construction to Span with extent == 0 or extent == dynamic.
- construct span from a range of pointer
- remove non const overload of the subscript operator
- remove non const overload of the data function
- implement subspan function
- implement missing first and last function of dynamic span
The Span class allows the creation of views over contiguous memory. The view
do not own memory, is typed and has a length. It can be used as a replacement of
the traditional pair of pointer and size in parameters or class fields.
Main operations:
- size(): return the lenght of the memory viewed
- empty(): return if the memory viewed is empty
- [index]: access elements viewed
- data(): return a pointer to the memory viewed.
- first(count): Create a subview from the first count elements.
- last(count): Create a subview from the last count elements.
- == and !=: compare two views or a view to array and return if they are equal or
not.
The Span class came in two flavors:
- Static size: The size is encoded in the Span type and it is as lightweitgh as
a single pointer,
- Dynamic size: The object can store arbitrary views and it costs one pointer
and the size of the view.
Vincent Coubard