Re: >FLOAT and the empty string

From	"Ed" <invalid@nospam.com>
Newsgroups	comp.lang.forth
Subject	Re: >FLOAT and the empty string
Date	2013-01-11 13:32 +1100
Organization	Aioe.org NNTP Server
Message-ID	<kcntm9$d6n$1@speranza.aioe.org> (permalink)
References	<kcnl77$r2q$1@dont-email.me>

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David N. Williams wrote:
> ...
> Gerry tells me that many system return true and convert the
> empty string to floating point zero.

This is classic behaviour in many programming languages
and the natural result of a string-to-number conversion algorithm.

Conversion routines don't test empty strings because it's
properly the task of the application.  It's a question of need.
Many an application will have rejected empty input well
before anything is passed to the number conversion routine.

For simple f/p apps that needed empty string testing I would
simply overload >FLOAT e.g.

    : STRING>FLOAT  ( a u -- r true | false )  dup if  >FLOAT  else  nip  then ;

Should >FLOAT handle leading/trailing blanks?  Not in my view
for the same reason.  It's extra work that's rarely needed and
simple to add yourself.

> "A string of blanks should be treated as a special case
> representing zero."
> ...
> But I don't see how a string of blanks can be empty!  Maybe it
> would be a good idea to specify that the empty string should be
> treated as a special case of a string of blanks.  But if so,
> shouldn't that be made explicit?

A string of blanks can be viewed as an extension of the empty
string i.e. both represent empty space.  Logically they should
return the same result.

Thread

>FLOAT and the empty string "David N. Williams" <williams@umich.edu> - 2013-01-10 19:09 -0500
  Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-11 13:32 +1100
  Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-11 11:11 +0000
    Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-11 23:10 +1100
      Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-23 16:21 +0000
        Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-25 13:35 +1100
          Re: >FLOAT and the empty string "Elizabeth D. Rather" <erather@forth.com> - 2013-01-25 21:33 +1300
            Re: >FLOAT and the empty string "Elizabeth D. Rather" <erather@forth.com> - 2013-01-25 21:41 +1300
            Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-28 22:39 +1100
              Re: >FLOAT and the empty string "Elizabeth D. Rather" <erather@forth.com> - 2013-01-28 10:36 -1000
                Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-29 11:11 +1100
                Re: >FLOAT and the empty string Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-29 03:19 -0600
                Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-30 11:03 +1100
  Re: >FLOAT and the empty string Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-11 05:39 -0600
    Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-23 16:31 +0000
      Re: >FLOAT and the empty string Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-23 10:44 -0600
        Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-23 17:21 +0000
          Re: >FLOAT and the empty string Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-23 11:50 -0600
            Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-24 13:09 +0000
              Re: >FLOAT and the empty string Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-24 09:22 -0600
                Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-24 16:16 +0000
          Re: >FLOAT and the empty string albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-01-24 03:45 +0000
            Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-24 12:56 +0000
        Re: >FLOAT and the empty string Alex McDonald <blog@rivadpm.com> - 2013-01-23 16:45 -0800
          Re: >FLOAT and the empty string Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-24 03:43 -0600
            Re: >FLOAT and the empty string Bernd Paysan <bernd.paysan@gmx.de> - 2013-01-24 16:59 +0100
  Re: >FLOAT and the empty string mhx@iae.nl (Marcel Hendrix) - 2013-01-11 19:32 +0200
    Re: >FLOAT and the empty string "David N. Williams" <williams@umich.edu> - 2013-01-20 10:30 -0500
      Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-21 16:51 +0000
      Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-23 11:42 +1100
        Re: >FLOAT and the empty string Mark Wills <forthfreak@gmail.com> - 2013-01-23 02:38 -0800
          Re: >FLOAT and the empty string anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-01-23 15:14 +0000
          Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-25 14:11 +1100
            Re: >FLOAT and the empty string Mark Wills <forthfreak@gmail.com> - 2013-01-24 23:33 -0800
              Re: >FLOAT and the empty string Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-25 02:52 -0600
              Re: >FLOAT and the empty string "Ed" <invalid@nospam.com> - 2013-01-28 22:53 +1100

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