Groups > comp.lang.java.programmer > #3647

Re: char to decimal

From	Jussi Piitulainen <jpiitula@ling.helsinki.fi>
Newsgroups	comp.lang.java.programmer
Subject	Re: char to decimal
Date	2011-05-06 10:30 +0300
Organization	University of Helsinki
Message-ID	<qotsjssmglj.fsf@ruuvi.it.helsinki.fi> (permalink)
References	(5 earlier) <9pednRnBeuxtPF_QnZ2dnUVZ_uGdnZ2d@earthlink.com> <ipuagg$iho$1@lust.ihug.co.nz> <ipupce$p2k$1@dont-email.me> <ipvd35$6ec$3@lust.ihug.co.nz> <4dc39812$0$8415$426a74cc@news.free.fr>

Show all headers | View raw

Mayeul writes:
> On 06/05/2011 01:49, Lawrence D'Oliveiro wrote:
> > In message<ipupce$p2k$1@dont-email.me>, Joshua Cranmer wrote:
> >
> >> On 05/05/2011 09:59 AM, Lawrence D'Oliveiro wrote:
> >>
> >>> In message<9pednRnBeuxtPF_QnZ2dnUVZ_uGdnZ2d@earthlink.com>, Patricia
> >>> Shanahan wrote:
> >>>
> >>>> There is a strong natural association between a character and the
> >>>> numeric value of its Unicode representation. There are several different
> >>>> ways of mapping between the two Boolean values and integers ...
> >>>
> >>> Only one “strong natural association”, though.
> >>
> >> 0,1; 1, -1; and 0, -1 all have arguments for their use.
> >
> > One of them is more useful than the others.
> 
> Says who, which one, on what grounds, and what do you make of the swaps?

Graham, Knuth, Patashnik, in Concrete Mathematics: A Foundation for
Computer Science, use [S] to stand for 0 when S is a false statement
and for 1 one when S is a true statement. They attribute the notation
to Iverson, who used round brackets. They find the mapping useful.

For example, the sign of x is [x > 0] - [x < 0].

For example, to add 1 to f(x) if n is divisible by m, you could write
f(x) + [n mod m > 0]. (In Java, use the per cent operator to get the
canonical element that is congruent to n modulo m.)

A widely used special case in mathematics is so called Kronecker's
delta that stands for [x = y]. (That's equality, not assignment.)

You get the other mappings quoted above as 1 - 2*[S] and -[S].

And whatever the two hash values were, call them F and T, you could
get them as F*[not s] + T*[s] where s is the truth value of the
statement S. (In Java, write !s for not s, I think.)

I am not saying that Java should do anything about all this. I am
saying that one of the mappings is already in general use elsewhere,
with established notations for it.

Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

char to decimal Dirk Bruere at NeoPax <dirk.bruere@gmail.com> - 2011-05-05 01:43 +0100
  Re: char to decimal Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2011-05-04 17:49 -0700
  Re: char to decimal Ian Shef <invalid@avoiding.spam> - 2011-05-05 01:06 +0000
    Re: char to decimal Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-05 20:03 +1200
      Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-05 07:03 -0400
        Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-05 11:18 +0000
          Re: char to decimal Patricia Shanahan <pats@acm.org> - 2011-05-05 06:11 -0700
            Re: char to decimal Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-06 01:59 +1200
              Re: char to decimal Mayeul <mayeul.marguet@free.fr> - 2011-05-05 16:53 +0200
                Re: char to decimal Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-06 11:49 +1200
                Re: char to decimal Mayeul <mayeul.marguet@free.fr> - 2011-05-06 08:46 +0200
                Re: char to decimal Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-06 18:43 +1200
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-06 06:52 -0400
                Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-06 11:39 +0000
              Re: char to decimal Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-05-05 14:13 -0400
                Re: char to decimal Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-06 11:49 +1200
                Re: char to decimal Mayeul <mayeul.marguet@free.fr> - 2011-05-06 08:47 +0200
                Re: char to decimal Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-06 18:43 +1200
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-06 06:54 -0400
                Re: char to decimal Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2011-05-06 10:30 +0300
              Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-05 17:05 -0400
            Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-05 14:56 +0000
              Re: char to decimal Paul Cager <paul.cager@googlemail.com> - 2011-05-05 11:48 -0700
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-05 17:06 -0400
                Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-05 21:28 +0000
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-05 17:32 -0400
                Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-06 08:31 +0000
          Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-05 17:04 -0400
      boolean to int : was char to decimal Jeff Higgins <jeff@invalid.invalid> - 2011-05-06 09:00 -0400
        Re: boolean to int : was char to decimal Patricia Shanahan <pats@acm.org> - 2011-05-06 06:54 -0700
        Re: boolean to int : was char to decimal markspace <-@.> - 2011-05-06 07:07 -0700
          Re: boolean to int : was char to decimal markspace <-@.> - 2011-05-06 08:30 -0700
        Re: boolean to int : was char to decimal Nigel Wade <nmw-news@ion.le.ac.uk> - 2011-05-06 15:35 +0100
        Re: boolean to int : was char to decimal Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-05-06 19:12 +0200
        Re: boolean to int : was char to decimal Jeff Higgins <jeff@invalid.invalid> - 2011-05-06 13:26 -0400
          Re: boolean to int : was char to decimal Jeff Higgins <jeff@invalid.invalid> - 2011-05-06 21:25 -0400
          Re: boolean to int : was char to decimal Jeff Higgins <jeff@invalid.invalid> - 2011-05-06 21:28 -0400
          Re: boolean to int : was char to decimal Michael Wojcik <mwojcik@newsguy.com> - 2011-05-09 12:51 -0400
            Re: boolean to int : was char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-09 23:54 +0000
            Re: boolean to int : was char to decimal Jeff Higgins <jeff@invalid.invalid> - 2011-05-09 20:51 -0400
              Re: boolean to int : was char to decimal Michael Wojcik <mwojcik@newsguy.com> - 2011-05-10 11:20 -0400
            Re: boolean to int : was char to decimal Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-10 13:47 +1200
              Re: boolean to int : was char to decimal Michael Wojcik <mwojcik@newsguy.com> - 2011-05-10 11:02 -0400
                Re: boolean to int : was char to decimal Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-11 14:05 +1200
                Re: boolean to int : was char to decimal Jeff Higgins <jeff@invalid.invalid> - 2011-05-11 08:11 -0400
  Re: char to decimal Dirk Bruere at NeoPax <dirk.bruere@gmail.com> - 2011-05-05 02:12 +0100
  Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-04 21:59 -0400
    Re: char to decimal Dirk Bruere at NeoPax <dirk.bruere@gmail.com> - 2011-05-05 16:14 +0100
      Re: char to decimal markspace <-@.> - 2011-05-05 11:20 -0700
        Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-05 17:10 -0400
          Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-05 22:00 +0000
            Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-05 18:20 -0400
          Re: char to decimal Dirk Bruere at NeoPax <dirk.bruere@gmail.com> - 2011-05-06 10:45 +0100
            Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-06 06:56 -0400
              Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-06 11:48 +0000
                Re: char to decimal Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-05-06 08:38 -0400
                Re: char to decimal Michael Wojcik <mwojcik@newsguy.com> - 2011-05-06 09:47 -0400
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-06 12:02 -0400
                Re: char to decimal Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-05-06 19:15 +0200
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-06 14:01 -0400
                Re: char to decimal Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-05-06 20:07 +0200
                Re: O/T linguistics (Was: char to decimal) Lew <noone@lewscanon.com> - 2011-05-06 15:28 -0400
                Re: O/T linguistics Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-05-06 21:44 +0200
                Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-06 23:57 +0000
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-06 12:00 -0400
              Re: char to decimal Dirk Bruere at NeoPax <dirk.bruere@gmail.com> - 2011-05-06 18:29 +0100
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-06 14:02 -0400
                Re: char to decimal Dirk Bruere at NeoPax <dirk.bruere@gmail.com> - 2011-05-07 01:09 +0100
                Re: char to decimal Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-07 00:18 +0000
                Re: char to decimal Lew <noone@lewscanon.com> - 2011-05-06 21:30 -0400
  Re: char to decimal Roedy Green <see_website@mindprod.com.invalid> - 2011-05-04 22:03 -0700
    Re: char to decimal "Nasser M. Abbasi" <nma@12000.org> - 2011-05-05 01:14 -0700
    Re: char to decimal Dirk Bruere at NeoPax <dirk.bruere@gmail.com> - 2011-05-05 16:15 +0100

csiph-web