[Python-Dev] Fraction arithmetic (Was: Decimal ... float comparisons in py3k) (original) (raw)

Paul Moore p.f.moore at gmail.com
Sat Mar 20 12:41:36 CET 2010


On 20 March 2010 04:20, Nick Coghlan <ncoghlan at gmail.com> wrote:

In the case of floats and Decimals, there's no ambiguity here that creates any temptation to guess - to determine a true/false result for a comparison, floats can be converted explicitly to Decimals without any loss of accuracy. For Fractions, the precedent has already been set by allowing implicit (potentially lossy) conversion to binary floats - a lossy conversion to Decimal wouldn't be any worse.

Hmm, given that a float can be converted losslessly to a fraction, why was the decision taken to convert the fraction to a float rather than the other way round?

I don't see a PEP for the fractions module, and my google-fu has failed to find anything. Was there a discussion on this?

Paul.



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