From: "trans.  (T. Onoma)" <transami@...>
Date: 2004-10-08T13:56:25+09:00
Subject: Re: Range behavior (Re: [RCR] New [] Semantics)

On Thursday 07 October 2004 11:42 pm, Yukihiro Matsumoto wrote:
| Hi,
|
| In message "Re: Range behavior (Re: [RCR] New [] Semantics)"
|
|     on Fri, 8 Oct 2004 11:08:54 +0900, "trans.  (T. Onoma)" 
<transami@runbox.com> writes:
| |Okay. In summary the problem centers around how to to define #===. When
| | you think about that you realize Range is serving two purposes which are
| | not perfectly compatible:
| |
| |   1) a discrete iterative set where .succ on first is used
| |      as generator and membership is defined like
| |
| |          val <=> succ </<= last
| |
| |   2) an interval where membership is determined like
| |
| |          val <=> first >= 0 && val <=> last </<= 0
|
| You have shown the behavior.  Then, what is the problem?
| Please be concrete.

Okay. The problem is that Range behavior is contradictory. Maybe this will 
help:

  def check(a)
    case a
    when 0..10 then
      true
    else
      false
    end
  end

  check(4.5)  # true or false ?

So #=== and case statements have two potential meanings for Range, and both 
are useful. Currently the answer is true --indicating a continuous range. But 
this is counter to the definition of a Range which, being dependent on #succ, 
is actually discrete. HTH.


| |Another problem is that numeric ranges, which are likely the most commonly
| |used by large margin, are *very* slow to determine #member?, --but they
| | don't need to be slow.
|
| Being slow IS the problem.

My problem? Your problem? Or Ruby's Problem? ;)

T.