[Python-Dev] Comparing heterogeneous types
ark at acm.org
Thu Jun 24 12:29:12 EDT 2004
> Well, even if for comparisons we treat floats as if they were exact,
> for other purposes I want to keep the association of "float" with
> "inexact" and "int/long" with "exact", and I'd rather not return an
> "exact" result from an operation involvin an "inexact" operand.
> (The alternative, introducing exactness as a separate concept from
> representation, is better in theory but in practice just complicates
> matters needlessly.)
However, I'm thinking less about exactness than I am about choosing the more
accurate of two possible representations for the result.
For example, in principle it should be possible to guarantee that x+0.0 == x
for all numeric values of x. The unanswered question in my mind is whether
such a guarantee carries other undesirable properties along with it.
Incidentally, right now I am leaning toward the believe that such a
guarantee *does* carry other undesirable properties along with it. For
example, consider 0L + 1e300. It is clear that in principle, no accuracy is
lost by returning the result of this addition as a long. It is equally
clear that in practice, it would be very slow.
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