From: Phrogz <phrogz@...>
Date: 2010-01-02T13:45:05+09:00
Subject: Re: Rounding float in ruby via .round

On Jan 1, 9:32 pm, Phrogz <phr...@mac.com> wrote:
> On Jan 1, 7:22 pm, pharrington <xenogene...@gmail.com> wrote:
>
> > On Jan 1, 9:13 pm, Phillip Gawlowski <p...@thimian.com> wrote:
>
> > > Which Ruby are you on?
>
> > <= 1.8.7
>
> You could do (untested on 1.8):
>
> if Float.instance_method(:round).arity == 0
>   class Float
>     alias_method :_orig_round, :round
>     def round( decimals=0 )
>       factor = 10**decimals
>       (self*factor)._orig_round / factor
>     end
>   end
> end
>
> Even gives you rounding to 'negative' decimal places, as in 1.9

Note that this gives you a Float as the result, which you may need to
use sprintf to display as desired. If you want something like
JavaScript's toFixed(), returning a string certain to be displaying
the precision you wanted, you might instead do (also untested):

class Numeric
  def round_to_str( decimals=0 )
    if decimals >= 0
      "%.#{decimals}f" % self
    else
      factor = 10**-decimals
      ((self/factor).round * factor).to_s
    end
  end
end