Groups > comp.lang.java.programmer > #8915

Re: prefix notation question

From	Chad <cdalten@gmail.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: prefix notation question
Date	2011-10-17 07:50 -0700
Organization	http://groups.google.com
Message-ID	<0135959f-5846-4869-9c5a-dd08998015e9@u13g2000vbx.googlegroups.com> (permalink)
References	(1 earlier) <BZGdnRzdc-qLOAbTnZ2dnUVZ_vydnZ2d@posted.palinacquisition> <0142e456-9e9a-4f71-adaa-5ea9cad35427@u9g2000vby.googlegroups.com> <qotbotg5c7i.fsf@ruuvi.it.helsinki.fi> <7889cbdf-4b32-413f-bae0-daea3814e85a@f13g2000vbv.googlegroups.com> <ae7f17fd-8825-4c5c-a185-0abed998aea5@a12g2000vbz.googlegroups.com>

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On Oct 17, 7:45 am, Chad <cdal...@gmail.com> wrote:
> On Oct 17, 7:39 am, Chad <cdal...@gmail.com> wrote:
>
>
>
>
>
> > On Oct 17, 12:06 am, Jussi Piitulainen <jpiit...@ling.helsinki.fi>
> > wrote:
>
> > > Chad <cdal...@gmail.com> writes:
> > > > On Oct 16, 8:46 pm, Peter Duniho <NpOeStPe...@NnOwSlPiAnMk.com> wrote:
> > > > > On 10/16/11 8:15 PM, Chad wrote:
>
> > > > > > I'm supposed to write a program that calculates arithmetic expressions
> > > > > > using prefix notation. The one example our professor gave us is
>
> > > > > > (+ (- 6) (* 2 3 4) (/ (+ 3) (* 1) (- 2 3 1)))
>
> > > > > > Which evaluated sucessively becomes..
>
> > > > > > (+ (- 6) (* 2 3 4) (/ 3 1 -2)) //<----I don't see how he arrives at
> > > > > > this expression
> > > > > > (+ -6 24 -1.5)
> > > > > > 16.5
>
> > > > > > I don't see how he gets (+ (- 6) (* 2 3 4) (/ 3 1 -2)) from (+ (- 6)
> > > > > > (* 2 3 4) (/ (+ 3) (* 1) (- 2 3 1)))
>
> > > > > Ask your professor.
>
> > > > I did. He told me to come by during his office hours. I told him I
> > > > couldn't because of work. He hasn't responded back.
>
> > > > Chad
>
> > > In (/ 3 1 -2), divided 3 by 1 and -2. Similarly in (- 2 3 1), subtract
> > > 3 and 1 from 2. This is the rule for two or more arguments to / and -.
>
> > > With one argument, like in (- 6), the rule is different and the
> > > notation means the appropriate inverse: additive inverse in case of -,
> > > multiplicative in case of /.
>
> > > The languages that use this notation tend to like -3/2 (an exact
> > > rational computed from exact rationals) more than -1.5 (typically an
> > > approximation).
>
> > But what happened to the (*3) that was in the original arithemtic
> > expression?
>
> I mean, what happened to (+3)? This obviously has to be account for
> somewhere.
>

Never mind. I was one again experiencing a brain lapse.

Chad.

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Thread

prefix notation question Chad <cdalten@gmail.com> - 2011-10-16 20:15 -0700
  Re: prefix notation question Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-10-16 20:46 -0700
    Re: prefix notation question Chad <cdalten@gmail.com> - 2011-10-16 20:58 -0700
      Re: prefix notation question Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-10-16 23:38 -0700
      Re: prefix notation question Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2011-10-17 10:06 +0300
        Re: prefix notation question Chad <cdalten@gmail.com> - 2011-10-17 07:39 -0700
          Re: prefix notation question Chad <cdalten@gmail.com> - 2011-10-17 07:45 -0700
            Re: prefix notation question Chad <cdalten@gmail.com> - 2011-10-17 07:50 -0700
              Re: prefix notation question Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2011-10-17 18:10 +0300
                Re: prefix notation question Chad <cdalten@gmail.com> - 2011-10-18 15:30 -0700
                Re: prefix notation question Roedy Green <see_website@mindprod.com.invalid> - 2011-10-18 19:40 -0700
  Re: prefix notation question Roedy Green <see_website@mindprod.com.invalid> - 2011-10-18 19:36 -0700

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