From: Markus <markus@...>
Date: 2004-10-05T23:33:48+09:00
Subject: Re: [RCR] New [] Semantics

     If I ever get past the parse.y hurdles, I plan to look at this.  I
think it's because ranges are actually a conflation of at least four
ideas:

      * ranges of Comparable objects, with the low less than the high,
        in which case <=> gives a quick member test
      * arcs of demi-circular array subscripts, where negative values
        "count back" from the end
      * Sets of discreet values than fall within one of the above
      * Arbitrary "starting" and "ending" tests

but I suspect this is not an exhaustive list.

     -- Markus

On Tue, 2004-10-05 at 02:19, trans. (T. Onoma) wrote:
> On Tuesday 05 October 2004 01:25 am, Markus wrote:
> > Typically, the versions of ruby I produce in these experiments are
> > killed by angry villages before they can show their essential
> > kindheartedness.  But I still hope.
> 
> I occurs to me that the angry villagers might be confused. The example of the 
> never ending
> 
>   (0..(10.0/0)).member?(4)
> 
> comes to mind. Why would this be an infinite loop? It must be trying to 
> generate the list before looking to see if 4 is in it (?) Are these ranges 
> that stupid? Even so, if it used succ to test this then it would take a while 
> to find out:
> 
> time ruby -e '(0..1000000000).member?(999999999)'
> 
> real    7m10.971s
> user    6m56.150s
> sys     0m0.617s
> 
> Yuk. But there is nothing one can do about it as long as one depends on #succ. 
> I suppose it's awfully clever and OOP and all to have any object supporting 
> <=> and succ work with ranges, but I wonder how much use they get outside of 
> numbers and occasional character ranges. In other words perhaps succ isn;t 
> the way to go (or perhaps a fallback) and a simple increment/decrement in the 
> Range itself would be more usable --then the above 7 minutes would be about 7 
> milliseconds.
> 
> T.