From: Brian Candler <B.Candler@...>
Date: 2004-10-05T20:20:44+09:00
Subject: Re: [RCR] New [] Semantics

On Tue, Oct 05, 2004 at 08:11:52PM +0900, Florian Frank wrote:
> >Yes, see adjacent thread. What it actually does is iterate all value 
> >from
> >start to end using succ, and set a flag to true when it finds a match 
> >(but
> >it doesn't break out of the loop when a match is found)
> 
> This seems the wrong thing to do. The documentation says:
> 
> ---------------------------------------------------------- Range#member?
>      rng.member?(val)   =>  true or false
> ------------------------------------------------------------------------
>      Return +true+ if _val_ is one of the values in _rng_ (that is if
>      +Range#each+ would return _val_ at some point).
> 
> I would think that it should return true, instead of going round in 
> circles.

I agree, although it's really only an optimisation, because other cases will
still give an infinite loop: in particular

      i = 1.0/0
      (2..i).member?(1)

So you have a halting problem instead :-)

> The Enumerable version works ok:
> 
> >> Enumerable.instance_method(:member?).bind(0..(1.0/0)).call(4)
> => true

Yes, it breaks out of the loop.

> I would prefer getting rid of the overriden member? implementation
> in range.c.

Or fixing it, but I'd also be happy to see it fall back to Enumerable, as
there's not much efficiency gain in implementing basically the same thing a
second time within range.c

Regards,

Brian.