Alternate signs in a range

[matovitch]

On Sunday, 26 January 2014 at 14:32:48 UTC, Stanislav Blinov 
wrote:
> On Sunday, 26 January 2014 at 14:24:35 UTC, matovitch wrote:
>
>> Well in a for loop, you only need one more index variable 
>> whereas here we store the whole index range.
>
> Not the *whole* range, that would be impossible since it's 
> infinite :) In this particular instance, index range is a 
> struct consisting of three variables: initial state (0), 
> current sequencer (n), and current element as cache. D ranges 
> are lazy. Well, most of them.

This is great ! Let's trust phobos then.