From: Logan Capaldo <logancapaldo@...>
Date: 2005-11-27T06:49:50+09:00
Subject: Re: string range membership

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On 11/25/05, Florian Frank <flori@nixe.ping.de> wrote:
>
> daz wrote:
>
> >Jim Weirich wrote
> >
> >
> >>How about "within?" for a value within a given range?
> >>
> >>
> >>
> >
> >   (0..5).within?(3)
> >
> >reads backwards, IMO compared to:
> >
> >   (0..5).include?(3)
> >
> >
> Yes, I agree. I think, just finding a new word for a method that does
> something, that used to have different names in the past, won't help.
> This has been tried, but it didn't work too well.
>
> Ruby's ranges have (at least) a dual nature:
> 1. as an interval (a, b) of values,
> 2. as a shortcut for a set of values { a, a.succ, a.succ.succ, ..., b }.
>
> I think "include?" is a good name for the 1. And 2 is very similar to 1,
> so people will easily confuse those names.
>
> What about using a bit of double dispatch here, like that:
>
> class Object
>   def element?(r)
>     r.find { |x| x =3D=3D self } ? true : false
>   end
> end
>
> "bb".element? "a".."zz" # =3D> true
>
> This doesn't read backwards, and the name conveys the meaning of set
> membership, as required by 2.
>
> Perhaps using another method than "find" for searching (that only
> defaults to "find") would make it possible, to provide an alternative
> implementation for datastructures, that can compute membership faster
> than O(n).
>
> --
> Florian Frank
>
>
>
I was going to suggest r.has_element?(x) for the equavilent of #member.
maybe r.surrounds?(x) for for #include. That one is not as good.

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