From: Yuri Leikind <YuriLeikind@...>
Date: 2001-11-14T01:29:31+09:00
Subject: [ruby-talk:25029] Set class in Ruby

Hello all Ruby coders,

Using Ruby for various tasks at work I 
often had to use hashes as sets. One day 
I coded a Set class as a sublass of Hash. 

Writing a Set class is no big deal,
a piece of cake, actually, but it saves 
me a _lot_ of time, as I can do such
high-level operations as subtracting sets,
intersecting them and so on.


I thought: Why doesn't Ruby have Set as a built-in class?
Smalltalk does have it. Before asking you this question
I searched this newsgroup archives and found this
interesting thread:

http://groups.google.com/groups?hl=en&th=17df256263eb21&rnum=1

Particularly, Dave Thomas suggested:

> Wouldn't it be clearer to define a new Set type, rather than new
> operations?

[cut]

> However, sometimes it's convenient to have Sets, collections where
> there's only ever one of each element. These have different semantics
> to arrays: they are not necessarily ordered, attempting to add an
> element doesn't necessarily increase the size, and so on.

So, why doesn't Ruby have Set as a built-in class?

-- 
Best regards,
Yuri Leikind