From: Ara.T.Howard@...
Date: 2004-10-16T03:34:36+09:00
Subject: Re: Rounding to X digits

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On Sat, 16 Oct 2004, trans.  (T. Onoma) wrote:

> On Friday 15 October 2004 11:14 am, Ara.T.Howard@noaa.gov wrote:| =C2=A0 =
=C2=A0jib:~/eg/ruby > cat truncate.rb| =C2=A0 =C2=A0class Float| =C2=A0 =C2=
=A0 =C2=A0def truncate sd =3D 2| =C2=A0 =C2=A0 =C2=A0 =C2=A0i =3D self.to_i=
| =C2=A0 =C2=A0 =C2=A0 =C2=A0prec =3D 10 ** sd| =C2=A0 =C2=A0 =C2=A0 =C2=A0=
fraction =3D (i.zero? ? self : (self / i) - 1)| =C2=A0 =C2=A0 =C2=A0 =C2=A0=
i + (fraction * prec).to_i / prec.to_f| =C2=A0 =C2=A0 =C2=A0end| =C2=A0 =C2=
=A0end|| =C2=A0 =C2=A0p(0.1 * (134.45/0.1).truncate) =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 #=3D> 134.4| =C2=A0 =C2=A0p((134.=
45 * (1/0.1)).truncate.to_f / (1/0.1)) =C2=A0 =C2=A0#=3D> 134.4|| =C2=A0 =
=C2=A0jib:~/eg/ruby > ruby truncate.rb| =C2=A0 =C2=A0134.4| =C2=A0 =C2=A013=
4.4
> Sorry, I don't follow. Isn't that answer incorrect? The mid-point should =
round up, not down. At least, that's what I was taught in school.
> T.

sorry-

not only did i post the wrong version, but mine clobbered the existing
truncate in Float, this ought to work:

   jib:~/eg/ruby > cat roundn.rb
   class Float
     def roundn sd =3D 2
       f =3D self.floor
       prec =3D 10.0 ** sd.to_i.abs
       frac =3D (f =3D=3D 0 ? self : self - f)
       f + (frac * prec).round / prec
     end
   end

   p(0.1 * (134.45/0.1).roundn)                   #=3D> 134.45
   p((134.45 * (1/0.1)).roundn.to_f / (1/0.1))    #=3D> 134.45

   jib:~/eg/ruby > ruby roundn.rb
   134.45
   134.45


regards.

-a

ps.  i'm cc'ing you directly to let you know your message ends up as one bi=
g
line in my mailer and i'm wondering if it's on my end or yours?

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| EMAIL   :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
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