Steven D'Aprano <steve+pyt...@pearwood.info> added the comment:
I see this has been rejected for the math module, but I wonder whether it
should be considered for Decimal? I recall Mark Dickinson demonstrating this
lovely little bit of behaviour:
py> from decimal import getcontext, Decimal
py> getcontext().prec = 3
py> x = Decimal('0.516')
py> y = Decimal('0.518')
py> (x + y) / 2
Decimal('0.515')
To prove its not a fluke, or an artifact of tiny numbers:
py> getcontext().prec = 28
py> a = Decimal('0.10000000000000000009267827205')
py> b = Decimal('0.10000000000000000009267827207')
py> a <= (a + b)/2 <= b
False
py> a = Decimal('710000000000000000009267827205')
py> b = Decimal('710000000000000000009267827207')
py> a <= (a + b)/2 <= b
False
Thoughts?
----------
nosy: +steven.daprano
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue36493>
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