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Groups > comp.lang.forth > #135284

Re: kForth-Win32 fix for decimal string to double float conversion

Date 2026-07-31 14:54 +1000
Subject Re: kForth-Win32 fix for decimal string to double float conversion
Newsgroups comp.lang.forth
References (2 earlier) <113nkmm$1u1in$1@dont-email.me> <nnd$245e5ae0$2ade0865@74903abd065dd450> <1142uj0$1m890$1@dont-email.me> <6a657bd2$1@news.ausics.net> <1144tts$2bpng$1@dont-email.me>
From dxf <dxforth@gmail.com>
Message-ID <6a6c2aa1$1@news.ausics.net> (permalink)
Organization Ausics - https://newsgroups.ausics.net

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On 26/07/2026 10:18 pm, Krishna Myneni wrote:
> On 7/25/26 22:15, dxf wrote:
>> On 26/07/2026 4:17 am, Krishna Myneni wrote:
>>> ...
>>> Run the fpio-tests for your input conversions to check. In your prior message, you showed me an output which is not even representable in double precision.
>>
>> FWIW running your test on my F87 EXT prec system produced 0 errors;
>> while F87 DBL prec resulted in 18 errors.
>>
> 
> That is expected. If you use 80-bit Extended Precision and then convert to 64-bit Double Precision, they should match. However, the tests in fpio-test.4th do not guarantee that the decimal string conversion is good to within 1 ulp for all 64 bits of the significand for the 80-bit format. The tests are specific to double precision format conversions.
> 
> 
>> I may try re-writing my input routine to parse from the other end but
>> my suspicion is it will be the same.  It may avoid having to SET-NEAR
>> but likely that's all.
>>
>> The IEEE spec for exact conversion was always going to be a high bar.
>> If one must have that, I'd rather use an EXT prec system and rename
>> DF@ DF! to F@ F! .
>>
> 
> David Gay's code, dtoa.c, is available to use for anyone interested in doing accurate decimal string to IEEE double precision format conversions and vice-versa. Your executable may grow by about 30--40K. I believe it supports 16 bit systems, but you may have to check.

I was aware of that solution though not the extent of the cost.  Considering my
entire forth runtime library is only 9K (3K being the f/p) it's quite a price
to pay to achieve IEEE compliance.  I've always wondered what possessed IEEE to
specify a conversion that exceeded the ability of the intrinsic precision to
readily provide.

I notice forths that employ the Intel FPU have largely abandoned IEEE's double
precision, instead opting for the internal 10-byte format.  None of those AFAIK
has made any attempt to achieve exact I/O conversion down to the last bit.  I
can fully appreciate their choice.  Equally so, C-based forths that need only
call in an existing library.

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kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-20 09:48 -0500
  Re: kForth-Win32 fix for decimal string to double float conversion albert@SPENARNC.XS4ALL.NL - 2026-07-21 11:40 +0200
    Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-21 06:20 -0500
      Re: kForth-Win32 fix for decimal string to double float conversion albert@SPENARNC.XS4ALL.NL - 2026-07-25 16:08 +0200
        Re: kForth-Win32 fix for decimal string to double float conversion peter <peter.noreply@tin.it> - 2026-07-25 17:07 +0200
          Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-25 13:22 -0500
            Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-25 13:30 -0500
        Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-25 13:17 -0500
          Re: kForth-Win32 fix for decimal string to double float conversion dxf <dxforth@gmail.com> - 2026-07-26 13:15 +1000
            Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-26 07:18 -0500
              Re: kForth-Win32 fix for decimal string to double float conversion dxf <dxforth@gmail.com> - 2026-07-31 14:54 +1000
                Re: kForth-Win32 fix for decimal string to double float conversion anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-07-31 08:35 +0000
                Re: kForth-Win32 fix for decimal string to double float conversion albert@spenarnc.xs4all.nl - 2026-07-31 12:05 +0200
                Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-31 07:54 -0500
                Re: kForth-Win32 fix for decimal string to double float conversion anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-07-31 16:55 +0000
                Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-31 14:40 -0500
                Re: kForth-Win32 fix for decimal string to double float conversion anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-08-01 08:23 +0000
                Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-01 06:42 -0500
    Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-21 11:30 -0500
      Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-21 14:47 -0500
  Re: kForth-Win32 fix for decimal string to double float conversion albert@SPENARNC.XS4ALL.NL - 2026-07-25 23:42 +0200
    Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-25 18:47 -0500
      Re: kForth-Win32 fix for decimal string to double float conversion albert@SPENARNC.XS4ALL.NL - 2026-07-26 13:11 +0200
  Re: kForth-Win32 fix for decimal string to double float conversion albert@SPENARNC.XS4ALL.NL - 2026-07-26 13:22 +0200
    Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-26 07:23 -0500
      Re: kForth-Win32 fix for decimal string to double float conversion albert@SPENARNC.XS4ALL.NL - 2026-07-26 20:13 +0200
        Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-07-27 12:20 -0500
  Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-11 07:24 -0500
  Re: kForth-Win32 fix for decimal string to double float conversion Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-08-24 18:55 -0500

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