On Sep 18, 2008, at 7:35 AM, Mark S. Miller wrote:
On Wed, Sep 17, 2008 at 10:53 PM, Maciej Stachowiak <[EMAIL PROTECTED]>
wrote:
I think it is a tenable position that 1.5m === 1.5000m based on the
"cohort" concept, since performing the same operation on both will
give answers that are in the same "cohort" equivalence class. But
1.5 / 10.0 != 1.5m / 10.0, and indeed, the answers would not even be
in the same cohort. A notion of 'cohort' equivalence class based on
correspondence in the abstract to the same real number but divorced
from the actual semantics of the programming language strikes me as
incoherent. I think such a notion of equivalence class only makes
sense if performing identical operations on members of the same
cohort gives answers which are in the same cohort.
Are -0 and 0 in the same cohort?
-0 === 0 is a quirk of the language that in my opinion we should not
repeat. Other than that oddity, === is a useful identity operator. As
Brendan said, 2^53 wrongs don't make a right.
But to answer your actual question, it seems to me they are not in the
same cohort in the same sense 1.5m and 1.500m are, since they may give
mathematically different answers under the same operation, answers
that differ in more than just precision.
Regards,
Maciej
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