From: "David A. Black" <dblack@...>
Date: 2005-11-29T01:07:05+09:00
Subject: Re: [BUG] string range membership

Hi --

On Tue, 29 Nov 2005, Yukihiro Matsumoto wrote:

> Hi,
>
> In message "Re: [BUG] string range membership"
>    on Tue, 29 Nov 2005 00:16:49 +0900, "Warren Brown" <warrenbrown@aquire.com> writes:
>
> |    OK, I think I see why they were changed to be the same, but I really
> |don't understand the choice of functionality that was kept.  For
> |everything except Ranges, #include? and #member? checks for set
> |membership.  In Ranges, #include? and #member? don't check for set
> |membership, they check for interval coverage instead.  This seems worse
> |than the original situation where at least #member? meant the same thing
> |everywhere.
>
> I don't remember exactly but it's for the sake of performance.  I've
> thinking about this issue for last few days, and it could be made
> better by treating numbers specially, just like we did for min and max
> in Range.

I think that as long as ranges have all of this array/set behavior --
as long as range and range.to_a share so much functionality -- ranges
will always feel like two different objects.  The whole idea of
"membership" in a range has always seemed a little strange to me.  I
guess I think of ranges as very different from arrays and sets.

> |    Anyway, could Range#include? and Range#member? be changed back to a
> |membership check and a new method be added to Range for interval
> |coverage, or would that break too much backwards compatibility?  Several
> |names come to mind for the new method: #between? (my personal favorite),
> |#betwixt? (kind of silly, but could be fun), #cover?, #surround?,
> |#bound?, #inside?, #within?, #in_range?, #in_interval?, #in?
> |
> |    If the current behavior of the Range methods can't be changed, names
> |for membership checks (not including #member? - yuck!) could be:
> |#among?, #amid?, #amidst?, #component?, #constituent?, #part?, #has?,
> |#in?
> |
> |    What do you think?
>
> Thank you for the candidates.  I'd like to hear opinion from others
> (especially from English speakers).

(0..5).to_a.include?(n) :-)

But seriously....  If it's a method of Range, then it has to be from
the range perspective, not the perspective of the argument.
#encompass? comes to mind.  There was an interesting discussion on IRC
about how to check for complete inclusion of one range in another.
#encompass?  could, ummm, encompass that:

   (0..5).encompass?(4)    # true
   (0..5).encompass?(5.1)  # false
   (0..5).encompass?(1..2) # true
   (1..2).encompass?(0..5) # false

etc.


David

-- 
David A. Black
dblack@wobblini.net