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Re: Floating point trouble with x86's extended precision
- From: dewar at gnat dot com (Robert Dewar)
- To: dewar at gnat dot com, fw at deneb dot enyo dot de
- Cc: gcc at gcc dot gnu dot org
- Date: Fri, 22 Aug 2003 23:13:48 -0400 (EDT)
- Subject: Re: Floating point trouble with x86's extended precision
>
> The current behavior sometimes results in objects which appear to
> spontaneously change their values between two read accesses (without
> any intermediate write access). I find it hard to believe that such
> indeterminacy is permitted by any language standard.
It is certainly permitted by the Fortran 77 standard
It is certainly permitted by the Ada 83 standard
It is certainly permitted by the Ada 95 standard (very explicitly)
As always it is better to go by what is in the standard rather than what
you believe (or find hard to believe).
With regard to the Fortran 77 standard, this is the subject of a well
known letter from Kahane, complaining of a bug, but in fact this was
not a bug according to the standard, though it certainly surprised
the writer of that letter :-)
I will let someone else quote language from the C or C++ standard that
would show that Florians universal quantification at least is correct
in existential form :-)