From: james.d.masters@...
Date: 2007-04-12T05:30:15+09:00
Subject: Re: ruby rounding?

On Apr 11, 11:17 am, "Kyle Schmitt" <kyleaschm...@gmail.com> wrote:
> Since there's so much development going on in Ruby currently, maybe
> something like this could be/should be added.

You could always create your own :).  Here is a something that I put
together.  There may be a better method.  The weird thing in the code
with comparing the remainder to 1e-9 is to deal with floating point
precision issues.  This may or may not be appropriate... I'm not a
rounding expert but it's worked in applications that I developed.

Anyway, here it is:

class Numeric
  def even_round()
    if ((self.truncate % 2 == 0) and ((self.remainder(1).abs -
0.5).abs < 1e-9))
      # integer portion is even and on 0.5 threshold
      self.truncate
    else
      # integer portion is odd or not on 0.5 threshold
      self.round
    end
  end
end

irb(main):012:0> a =  [-5.0, -4.5, -4.0, -3.5, -3.0, -2.5, -2.0, -1.5,
-1.0, -0.5, 0.0, 0.5,  1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5]
=> [-5.0, -4.5, -4.0, -3.5, -3.0, -2.5, -2.0, -1.5, -1.0, -0.5, 0.0,
0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5]
irb(main):013:0> a.map {|e| e.even_round}
=> [-5, -4, -4, -4, -3, -2, -2, -2, -1, 0, 0, 0, 1, 2, 2, 2, 3, 4, 4,
4]