From: "trans.  (T. Onoma)" <transami@...>
Date: 2004-10-05T19:38:01+09:00
Subject: Re: [RCR] New [] Semantics

On Tuesday 05 October 2004 05:59 am, Brian Candler wrote:
> Yes, but what you probably want is 'include?' rather than 'member?'

Certainly helps to know the distinction (which in unintuitive btw)

> Both Range#include? and Range#member? override the methods mixed in from
> Enumerable, where those methods are just synonyms for each other.
>
> This is certainly confusing!

Amazing how even the simple things get that way!

> I'd say if you want to iterate over the range, then use Enumerable#find or
> Enumerable#find_all as appropriate, then get rid of this distinction.

Understandable. #member? should just be an alias for #find then and use 
#between? for other need. At least, that seems the most consistant.

> > 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.
>
> If you're going to rely on increment/decrement then I'm pretty sure you can
> also rely on the mathematic properties of < and >, i.e. just compare the
> boundary values as 'include?' does.
>
> Besides,
>   a = a.succ
> and
>   a = a + 1
> take almost identical amounts of time, since even '+ 1' involves a method
> dispatch:
>   a = a.send(:+,1)

With inc/dec modulo can be used. Something like:

  def member?(e)
    return ( (((e + self.begin) % @increment) == 0) && self.between?(e) )
  end

T.