From: Michael Ulm <michael.ulm@...>
Date: 2007-10-25T15:40:00+09:00
Subject: Re: Intervals in Ruby

Steven D'Aprano wrote:
> Howdy,
> 
> I'm not a Ruby developer *at all*, I use Python, but this is not flame-
> bait. I'm interested in how Ruby folks find using intervals.
> 
> In Python, we deal with integer ranges virtually exclusively with the 
> range() function. range() always results in a half-open interval:
> 
> range(5) => 0, 1, 2, 3, 4
> range(1, 5) => 1, 2, 3, 4
> range(4, -1, -1) => 4, 3, 2, 1, 0
> 
> The start argument is always included, the end argument is never 
> included, and there is an optional step size (defaults to 1).

If there is only one kind of range to be supported (which I understand
to be in sync with the Python philosophy), I agree that half-open
intervals are the way to go. 

> 
> I understand that in Ruby you have quite a few choices, some of which are 
> half-open like Python, some of which are closed:
> 
> 0..5 => 0, 1, 2, 3, 4, 5
> 0...5 => 0, 1, 2, 3, 4

The two different ranges are nice-to-have, because sometimes the closed
interval is the right thing to use. I'd have exchanged the syntax 'though.
Having said that, I have never had a problem distinguishing the two.
> 
> 5.downto(1) => 5, 4, 3, 2, 1
> 1.upto(5) => 1, 2, 3, 4, 5
> 5.times() => 0, 1, 2, 3, 4
> 5.step(11, 3) => 5, 8, 11
--snip--

This is not really a range, but the Ruby Way of looping; it is what made me
fall in love with Ruby in the first place. For me, it is one the most
beautiful aspects of any programming language that I know.

Best regards,

Michael