[Python-Dev] PEP239 (Rational Numbers) Reference Implementation and new issues
Erik Max Francis
max at alcyone.com
Fri Oct 4 04:18:31 CEST 2002
Greg Ewing wrote:
> My own faded memory says: L'Hopital's Rule. Differentiate top
> and bottom and take the limit of that instead. Repeat until
> top and bottom don't both go to 0.
This also works for other indeterminate limits, e.g., oo/oo. However
there's an important distinction here that's being left out. Infinity
and indeterminacy, strictly speaking, only apply when _limits_ are being
taken. If there's no limit that you're taking that gives you 1/0 when
naively substituted, then you're not talking about something that's
"infinite" or "indeterminate," you're talking about something that's
> There's no doubt some terribly good reason why this works,
> but I can't remember it, if I ever knew...
Well, L'Hopital's rule has a proof associated with it. Either you can
follow the proof to enlightenment or just trust in the fact that it
really does work.
Erik Max Francis / max at alcyone.com / http://www.alcyone.com/max/
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