On 2010-03-16 07:35 AM, Dave Angel wrote:
Carl Banks wrote:
On Mar 15, 4:34 pm, JLundell <jlund...@pobox.com> wrote:
It's also unfortunate that Python doesn't have an approximately-equal
operator; it'd come in handy for floating-point applications while
preserving hash. If only there were a ~=r ≈ operator I could
overload. And ~ is unary, so no joy.
One problem with it is that there's no way to make it universal;
different appiplications have different ideas of close. Conceivably
it could be usefully defined for a user type though..
Bacause of this problem almost no languages have an almost equal
operator. I'm curious what languages do, of if there are any with a
trinary operator that also takes a threshold.
Carl Banks
If I recall correctly, APL has a *fuzz* value, which is used in all(?)
comparisons. But I do not recall anything about how it was defined. I do
recall that you could change the threshold, and suspect it was relative
to the operands. For symmetry, it would probably have to be relative to
the average of the two values, or some such.
The problem is that frequently there is no system-wide fuzz value which is
appropriate for all comparisons in a given program. You need to choose the right
value for each comparison. Consequently, you might as well use a function
instead of an operator and a global variable.
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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