From: Robert Klemme <shortcutter@...>
Date: 2011-02-02T00:26:01+09:00
Subject: Re: Ruby Range issues

On Tue, Feb 1, 2011 at 3:33 PM, Ray Bovet <Ray@bovet.org> wrote:
> Since I haven't posted to this group in the past 5 years or so, let me start
> by saying how much I enjoy using Ruby!  My comments below reflect my desire
> to see a couple of small issues improved in this extraordinary language!
>
>
> The first is a requested feature (which works in 1.8.7 but not in
> 1.9.2p136), while the second appears to me to be a bug that exists in both
> 1.8.7 and 1.9.2:
>
> 1. Range.step says (per PickAxe 3) that it works with range elements that
> support .succ, or with numbers.  It would be nice to have it work with
> elements that support .succ, /or with elements that support adding a number
> to them/.  This would allow stepping through time ranges, for example.

Not sure this is a good idea.  After all, if +1 would be the "default"
increment for a class #succ would have been implemented that way.  In
absence of a #succ implementation a Range cannot do any assumption as
to how get the next value - that's the exact reason why there is a
method #succ.  You could as well wrap a Time instance in something
that implements #succ accordingly.

irb(main):001:0> require 'delegate'
=> true
irb(main):002:0> class TD < SimpleDelegator
irb(main):003:1> def succ;self.class.new(__getobj__ + 1); end
irb(main):004:1> end
=> nil
irb(main):005:0> t = TD.new(Time.now)
=> 2011-02-01 16:23:24 +0100
irb(main):006:0> t.succ
=> 2011-02-01 16:23:25 +0100
irb(main):007:0> t.succ.succ
=> 2011-02-01 16:23:26 +0100

> 2. Range.step where the end is specified to be excluded ( '...') on floats
> seems to exclude the last value that should be included.  For example:
>    ( 1.0 ... 5.01).step( 2) {|x| puts x}
>    outputs 1.0 and 3.0 but not 5.0.
>    Interestingly, ( 1.0 ... 5.01).cover?( 5.0) returns true, as it should!

Sounds like a bug which is not present in 1.9.2:

irb(main):008:0> (1.0..5.1).step(2).to_a
=> [1.0, 3.0, 5.0]
irb(main):009:0> (1.0..5.01).step(2).to_a
=> [1.0, 3.0, 5.0]

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/