The rfind challenge

[H. S. Teoh]

On Tue, Jan 15, 2013 at 06:03:06PM +0100, Phil Lavoie wrote:
[...]
> An addition to this solution could be another new primitive:
> reverse:
> 
> Pseudo:
>   original = range.save
>   reversed = range.reverse //Permanently invert start an end. I
> think this is feasible for all bidirectional ranges. Still a
> bidirectional range.
[...]

I like this very much, actually. I think .reverse is much more useful
than .back and .popBack. I mean, how many algorithms actually use .back
and .popBack? Probably less than a handful, if any. Most algorithms use
.front and popFront().

Viewed in that light, what then is a bidirectional range, if not a range
where you can swap the direction of iteration? That is, we can redefine
a bidirectional range to be one that implements .reverse, with the
property that R.reverse.reverse == R. Get rid of .back and .popBack,
which hardly anybody uses anyway. It simplifies the range API
significantly, and makes rfind implementable in terms of primitives.


T

-- 
Ruby is essentially Perl minus Wall.