From: Brian Candler <B.Candler@...>
Date: 2004-10-05T19:05:29+09:00
Subject: Re: Too Many Ways?

On Tue, Oct 05, 2004 at 06:28:35PM +0900, trans.  (T. Onoma) wrote:
> > Looking at the source, I see that Range#member? iterates using the 'each'
> > function, whereas Range#include? just compares against the start and end
> > values.
> >
> > I think it's a bug that Range#member? doesn't do a 'break' when it finds a
> > match. OTOH, I guess it's pretty dubious to be relying on Enumerable-type
> > methods over an infinite enumeration :-)
> 
> I see! Well, yes it is a bug (IMHO). Moreover #include? should be the same as 
> #member?  According to this, what #include? is doing now it really something 
> different: #between?
> 
> irb(main):002:0> r = (0...10)
> => 0...10
> irb(main):003:0> r.include?(4.3)
> => true
> 
> Which isn't really right.

Errm, well it looks right to me. If you're saying that the range 0...10 is
actually the set of integers 0,1,2,3,4,5,6,7,8,9, then 4.3 is not a member
of that set; but if you consider it as a continuous range along the number
line, then 4.3 is included within that range. And Ruby does indeed recognise
the distinction:

irb(main):001:0> r = (0...10)
=> 0...10
irb(main):002:0> r.include?(4.3)
=> true
irb(main):003:0> r.member?(4.3)
=> false

> I'll look at it some more later. Do you see anything in particular that's 
> problematic with it?

I think it will work fine. The problem will be that many more cases will
turn up where Infinity should be treated as a special case, for consistency.

  a[2,Infinity]
  a[2..Infinity]   # currently gives RangeError: float Inf out of range of integer
... probably lots of others

And unfortunately we still don't eliminate the smelly ranges where last <
first.

  a = "mystring"
  a[2..-1]

Regards,

Brian.