Greg Ewing wrote:
Steven D'Aprano wrote:
it should be obvious in the same way that string concatenation is
different from numerical addition:
1 + 2 = 2 + 1
'1' + '2' != '2' + '1'
However, the proposed arithmetic isn't just non-
commutative, it's non-associative, which is a
much rarer and more surprising thing. We do
at least have
('1' + '2') + '3' == '1' + ('2' + '3')
But we don't have:
(1e40 + -1e40) + 1 == 1e40 + (-1e40 + 1)
Non-associativity is what makes for floating point headaches.
To my knowledge, floating point is at least commutative.
--Scott David Daniels
scott.dani...@acm.org
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