E.P E. E.EXACT

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	E.P E. E.EXACT
Date	2026-08-05 18:02 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2026Aug5.200203@mips.complang.tuwien.ac.at> (permalink)

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Gforth now has three new words:

E. ( r -- ) prints an FP number r in a format that is understood by
   Gforth's text interpreter and produces the same number.  Tries to
   produce short outputs.

E.EXACT ( r -- ) prints an FP number, showing all (possibly hundreds)
   of the mantissa digits.

E.P ( r u -- ) prints an FP number with at most u (or, if that saves
   printing an exponent, u+1) mantissa digits.

Example usage and output (as comment):

: s-as-f {: w^ n :} n f@ ;
0e e.         \ 0e ok
1e e.         \ 1e ok
0.1e e.       \ .1e ok
0.00005e e.   \ .00005e ok
0.000005e e.  \ 5e-6 ok
2000e e.      \ 2e3 ok
20000e e.     \ 2e4 ok
1 s-as-f e.   \ 5e-324 ok

Note that the latter number takes more than 700 digits when printed
with e.exact; only one mantissa digit is necessary to distinguish it
from other numbers, because the next FP number has a value close to
1e-323.

0e e.exact        \ 0e ok
1e e.exact        \ 1e ok
0.1e e.exact      \ .1000000000000000055511151231257827021181583404541015625e ok
0.00005e e.exact  \ .0000500000000000000023960868011929647991564706899225711822509765625e ok
0.000005e e.exact \ 5.0000000000000004090152695701565477293115691281855106353759765625e-6 ok
2000e e.exact     \ 2000e ok
20000e e.exact    \ 20000e ok
2e23 e.exact      \ 199999999999999983222784e ok

Note that the difference between the input and the output in these
cases comes from the input side (>FLOAT): 0.1e, 0.00005e, 0.000005e
and 2e23 cannot be represented exactly in binary64 (IEEE
double-precision) FP, do >FLOAT produces the FP number closest to the
decimal representation.  E.EXACT then prints all the digits of this
number, while E. prints a number that is close and consumes as few
digits as possible.

0e 6 e.p        \ 0e ok
1e 6 e.p        \ 1e ok
0.1e 6 e.p      \ .1e ok
0.00005e 6 e.p  \ .00005e ok
0.000005e 6 e.p \ 5e-6 ok
2000e 6 e.p     \ 2000e ok
20000e 6 e.p    \ 20000e ok
1234567e 6 e.p  \ 1234567e ok

The last case is one where we prefer to print one additional mantissa
digit and leave the exponent away instead of writing 1.23457e6.

You can find the source code at
<https://cgit.git.savannah.gnu.org/cgit/gforth.git/tree/edot.fs>

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: https://forth-standard.org/
EuroForth 2026 CFP: http://www.euroforth.org/ef26/cfp.html

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E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-05 18:02 +0000
  Re: E.P E. E.EXACT Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-06 08:13 -0500
    Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-06 14:00 +0000
      Re: E.P E. E.EXACT Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-06 10:45 -0500
        Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-06 15:58 +0000
          Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-06 17:20 +0000
        Re: E.P E. E.EXACT marcel hendrix <mhx@iae.nl> - 2026-08-06 21:05 +0200
          Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-06 20:38 +0000
          Re: E.P E. E.EXACT Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-06 18:44 -0500
          Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-07 11:03 +1000
            Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-07 10:11 +0000
              Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-08 14:39 +1000
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-08 06:32 +0000
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-09 04:50 +1000
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-10 20:01 +1000
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-10 18:06 +0000
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-10 17:24 +0000
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-11 14:01 +1000
                Re: E.P E. E.EXACT Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-10 22:10 -0500
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-11 04:56 +0000
                Re: E.P E. E.EXACT Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-11 22:16 -0500
                Re: E.P E. E.EXACT Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-12 05:47 -0500
                Re: E.P E. E.EXACT peter <peter.noreply@tin.it> - 2026-08-12 18:03 +0200
                Re: E.P E. E.EXACT Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-12 11:48 -0500
                Re: E.P E. E.EXACT marcel hendrix <mhx@iae.nl> - 2026-08-08 09:14 +0200
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-08 09:40 +0000
                Re: E.P E. E.EXACT marcel hendrix <mhx@iae.nl> - 2026-08-08 15:26 +0200
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-10 16:43 +0000
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-09 13:43 +1000
                Re: E.P E. E.EXACT marcel hendrix <mhx@iae.nl> - 2026-08-09 07:19 +0200
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-10 19:15 +1000
                Re: E.P E. E.EXACT marcel hendrix <mhx@iae.nl> - 2026-08-10 13:17 +0200
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-10 22:59 +1000
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-10 23:54 +1000
                Re: E.P E. E.EXACT marcel hendrix <mhx@iae.nl> - 2026-08-10 20:42 +0200
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-11 17:10 +1000
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-12 14:04 +1000
                Re: E.P E. E.EXACT albert@spenarnc.xs4all.nl - 2026-08-22 16:43 +0200
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-22 15:47 +0000
                Re: E.P E. E.EXACT albert@spenarnc.xs4all.nl - 2026-08-22 18:27 +0200
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-22 16:40 +0000
                Re: E.P E. E.EXACT albert@spenarnc.xs4all.nl - 2026-08-22 19:42 +0200
                Re: E.P E. E.EXACT anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-22 18:03 +0000
                Re: E.P E. E.EXACT albert@spenarnc.xs4all.nl - 2026-08-22 22:56 +0200
                Re: E.P E. E.EXACT marcel hendrix <mhx@iae.nl> - 2026-08-23 00:50 +0200
                Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-23 12:25 +1000
                Re: E.P E. E.EXACT Hans Bezemer <the.beez.speaks@gmail.com> - 2026-08-09 14:52 +0200
            Re: E.P E. E.EXACT Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-07 07:50 -0500
              Re: E.P E. E.EXACT dxf <dxforth@gmail.com> - 2026-08-08 12:33 +1000
                Re: E.P E. E.EXACT albert@spenarnc.xs4all.nl - 2026-08-22 17:01 +0200
          Re: E.P E. E.EXACT albert@spenarnc.xs4all.nl - 2026-08-22 16:15 +0200

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