From: Glenn Jackman <glennj@...>
Date: 2009-07-23T23:40:04+09:00
Subject: Re: Bug Rounding Floats? (9.245 * 100).round => 924? S/B 925!

At 2009-07-22 03:22PM, "ddoherty03" wrote:
>  On Jul 22, 1:13�pm, Glenn Jackman <gle...@ncf.ca> wrote:
> > A workaround, convert the expression to a string and back to a number:
> > � � num = Float("%.1f" % (9.245 * 100)).round
> > � � puts "yippee" if num == 925
>  
>  Glenn,
>  
>  Thanks for the explanation.  If I could pick your brain for a second
>  on how to generalize your workaround, I would greatly appreciate it.
>  
>  Here is how I tried to implement the "nround" method.
>  
>  ######################################
>  class Float
>    def nround(n = 0)
>      (self * 10.0 ** n).round / 10.0 ** n
>    end
>  end
>  ######################################
>  
>  My issue is getting the workaround to deal with the parameter n
>  properly.

Taking Bil Kleb's advice, 

    require 'bigdecimal'
    require 'bigdecimal/util'

    class Float
      def nround(n=0)
        (self.to_d * (10.0**n).to_d).round.to_f / 10.0**n
      end
    end

    p 9.245.nround(2)  # => 9.25

-- 
Glenn Jackman
    Write a wise saying and your name will live forever. -- Anonymous