From: Robert Klemme <shortcutter@...>
Date: 2011-04-14T22:28:44+09:00
Subject: Re: Exclusive float range, Range#step result in counterintuitive result

On Thu, Apr 14, 2011 at 2:42 PM, Joey Zhou <yimutang@gmail.com> wrote:
> Hi everybody,
>
> I find that:
>
> if
>  range.exclude_end? == true
> and
>  [begin_obj, end_obj, step].grep(Float) != []
> and
>  [begin_obj, end_obj, step].any? {|f| f != f.to_i}
> then
>  # result will miss the last one
> end
>
> for example:
>
> p (1...6.3).step.to_a # => [1.0, 2.0, 3.0, 4.0, 5.0], missing 6.0
> p (1.1...6).step.to_a # => [1.1, 2.1, 3.1, 4.1], missing 5.1
> p (1...6).step(1.1).to_a # => [1.0, 2.1, 3.2, 4.300000000000001],
> missing 5.4
>
> p (1.0...6.6).step(1.9).to_a # => [1.0, 2.9], missing 4.8
> p (1.0...6.7).step(1.9).to_a # => [1.0, 2.9, 4.8], 6.7 == 4.8 + 1.9,
> it's ok
>
> The results seem so counterintuitive, is it a bug? Maybe I should report
> it?

Hmmm...  Float and Range generally don't mix very well.  Considering
this the results seem at least consistent - if not expected:

irb(main):001:0> (1.0...6.6).step(1.9).to_a
=> [1.0, 2.9]
irb(main):002:0> (1.0..6.6).step(1.9).to_a
=> [1.0, 2.9, 4.8]

Line 2 cannot go beyond 4.8 because then it would pass 6.6, so the
last value which can really be returned is 4.8.  The third dot removes
that value from the list.

It's at least a tad weird.  +0.5 for opening a bug.

Kind regards

robert

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