[Python-ideas] Python Numbers as Human Concept Decimal System

[Paul Du Bois]

On Fri, Mar 7, 2014 at 6:15 PM, Guido van Rossum <guido at python.org> wrote:

> Or, Decimal(repr(some_float)), which DWIM.
>

Because I haven't seen anyone else bring this up, using a non-exact
conversion breaks the invariant "Decimal(f)==f".

There are so many pairs of numeric types that break that invariant that it
might not be a big deal; but in all other cases the invariant is broken
because it is theoretically impossible.

from decimal import Decimal
f = 2.2
print(Decimal(f)==f)
print(Decimal(repr(f))==f)


p
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