[issue1580] Use shorter float repr when possible

[Noam Raphael]

Noam Raphael added the comment:

2007/12/18, Raymond Hettinger <report at bugs.python.org>:
> The 17 digit representation is useful in that it suggests where the
> problem lies.  In contrast, showing two numbers with reprs of different
> lengths will strongly suggest that the shorter one is exactly
> represented.  Currently, that is a useful suggestion, 10.25 shows as
> 10.25 while 10.21 shows as 10.210000000000001 (indicating that the
> latter is not exactly represented).  If you start showing 1.1 as 1.1,
> then you've lost both benefits.

Currently, repr(1.3) == '1.3', suggesting that it is exactly
represented, which isn't true. I think that unless you use an
algorithm that will truncate zeros only if the decimal representation
is exact, the suggested algorithm is less confusing than the current
one, in that it doesn't suggest that 1.3 is exactly stored and 1.1
isn't.

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<http://bugs.python.org/issue1580>
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