From: Florian Frank <flori@...>
Date: 2005-11-26T07:47:30+09:00
Subject: Re: string range membership

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 == self } ? true : false
  end
end

"bb".element? "a".."zz" # => 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