Re: The disturbing myth of Eiffel portability

["Norman H. Cohen" <ncohen@watson.ibm.com>]

Keith Thompson wrote:

> Any bets on whether Ada 200Y mandates (or at least strongly encourages)
> IEEE arithmetic?

Ada 95 already explicitly acknowledges the IEEE standard (referring to
it as IEC 559:1989 rather than IEEE 754, since Ada 95 is itself an
ISO/IEC standard).  The attribute S'Signed_Zeros is defined in A.5.3(13)
in terms of the floating-point standard.  A.10.9(35) gives
implementation permission for floating-point Put and Get to have some
textual representation of NaNs and infinities.  In the Numerics Annex,
G.1.1(56,57) gives advice in implementing complex arithmetic in a manner
that will produce the expected results in "systems that, in the future,
support an Ada binding to IEC559:1989".

Of course the intent here is to allow rather than require support of
IEEE arithmetic.  I think implementors can be counted on to provide
IEEE-based floating-point types (at the very least, types whose behavior
is consistent with SOME specified IEEE mode) on those targets with
IEEE-compliant hardware.

Perhaps a complete binding to the full floating-point standard (with
control over rounding modes and NaN signaling modes) will be adopted as
a secondary standard, implementable either directly in hardware or by
software emulation, depending on the target.  This need not await Ada
200Y (a project that so far exists only in the imaginations of some
participants in this newsgroup).

> FIJAGDWOL

I don't follow.  Could you please elaborate?

-- 
Norman H. Cohen
mailto:ncohen@watson.ibm.com
http://www.research.ibm.com/people/n/ncohen