[Python-Dev] Rational approximation methods (original) (raw)

Paul Moore p.f.moore at gmail.com
Sun Jan 20 14:28:27 CET 2008

On 19/01/2008, Jeffrey Yasskin <jyasskin at gmail.com> wrote:

The first returns the closest rational whose denominator is less than a given integer. [...] The second returns the simplest rational within some distance.

Both of these are likely to be of limited use. The most common usage I know of is to make a "sensible" rational from a float (i.e., a DWIM style conversion 0.1 -> 1/10) or to provide readable output. On the other hand, both are subtle to implement, so having a standard implementation saves people having to code (and debug) their own.

I suspect that simplest within a particular distance is the form that is most often wanted, but I don't have any good evidence for that feeling. Putting both in might help people to realise that there is a choice.

Given that you have implemented them, I'd say leave them in. And I like the names trim and approximate, as given in the code you referenced.

Paul.

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