RFC on range design for D2

[Manfred_Nowak]

Andrei Alexandrescu wrote:

>> 1)
> There are numerous collections and ranges to be defined

You are right. A reversable range can be built with the designed 
primitives. But this also holds for the `Retro'-type.

>> 2)
> I used these:
> leftToLeft

Much better, but did you notice, that you used the directionless words 
"beginning" and "end" to describe their semantics? That's why I used 
"B" and "E". With directions in the names one might be forced to make 
wrappers for not being irritated by the directions in case they do not 
fit.

Ex.: Imagine a 4d-matrix in which a 3d-range is defined diagonally to 
three of the axis of the 4d-matrix. What is left respective right of 
such a range?  

3) casting

On second read I miss some words about explicite and implicite casting 
possibilities between the five types of ranges. 

-manfred


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