From: "trans.  (T. Onoma)" <transami@...>
Date: 2004-10-15T23:28:13+09:00
Subject: Re: Rounding to X digits

On Thursday 14 October 2004 01:55 pm, Markus wrote:
| Here's mine (with a few extras):
|
| class Numeric
|     def iff(cond)
|         cond ? self : self-self
|         end
|     def to_the_nearest(n)
|         n*(self/n).round
|         end
|     def aprox(x,n=0.001)
|         (to_the_nearest n) == (x.to_the_nearest n)
|         end
|     def at_least(x); (self >= x) ? self : x; end
|     def at_most(x);  (self <= x) ? self : x; end
|     end
|

|     def to_the_nearest(n)
|         n*(self/n).round
|         end
  def round_to_nearest( n=0.01 )
    (self * (1/n)).round.to_f / (1/n)
  end

For some reason they don't give the exact same answer. Try an edge case.

  irb(main):066:0> 0.1 * (134.45/0.1).round
  => 134.4
  irb(main):067:0> (134.45 * (1/0.1)).round.to_f / (1/0.1)
  => 134.5

T.