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mapping 754R to specific languages
All modes could be static or dynamic language features, and could be
implemented with static or dynamic types of hardware.
What distiguishes reproducibility from other modes such as rounding and
even alternate exception handling (to some extent) is that it does not
map to hardware structures. You do however have a point with:
because that implies generating many alternate sequences of code, of
which one will be selected at run time according to the dynamic modes
in effect when called.
I suppose that method would be applicable: generate two code sequences,
one of which corresponds to what could have been provided in a statically
bound and scoped environment.
You also addressed separate compilation to my satisfaction.
What remains to be done is to describe the limitations that the user
who is concerned about reproducibility has to be aware of. It has
occurred to me that most of my objections could be handled by documented
restrictions -- my concern was that the restrictions might leave no room
for writing the intended programs.
As for PL/I and widenTo, I have to confess that I have not used PL/I in
almost 30 years, so the issue of x87-like intermediaries hadn't come up.
I remember PL/I as having very definite type-coercion rules covering
decimal vs binary as well as integer vs real, and type sizes -- but don't
ask for details! My point was that if a language does not leave any
choice to the implementation, then widenTo should not be forced upon it.
Michel.
Sent: 2007-07-30 03:11:51 UTC