Message 91888 - Python tracker

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In-reply-to
Author	mark.dickinson
Recipients	mark.dickinson, steve21
Date	2009年08月23日.15:22:50
SpamBayes Score	1.0425647e-06
Marked as misclassified	No
Message-id	<1251040973.02.0.949878652648.issue6765@psf.upfronthosting.co.za>

Content
Well, that's floating-point arithmetic for you. log(x, y) simply computes log(x)/log(y) behind the scenes; since both log computations and the floating-point division can introduce errors, the result will frequently not be correctly rounded. I don't really see the benefit of special-casing log(x, 10). In what circumstances does it matter that log(x, 10) != log10(x)? I could understand people being upset that log(10**n, 10) doesn't return n exactly, but that's what log10 is there for. See also the discussion in issue 3724.

Content

Well, that's floating-point arithmetic for you. log(x, y) simply computes 
log(x)/log(y) behind the scenes; since both log computations and the 
floating-point division can introduce errors, the result will frequently 
not be correctly rounded.
I don't really see the benefit of special-casing log(x, 10). In what 
circumstances does it matter that log(x, 10) != log10(x)? I could 
understand people being upset that log(10**n, 10) doesn't return n 
exactly, but that's what log10 is there for.
See also the discussion in issue 3724.

History
Date	User	Action	Args
2009年08月23日 15:22:53	mark.dickinson	set	recipients: + mark.dickinson, steve21
2009年08月23日 15:22:53	mark.dickinson	set	messageid: <1251040973.02.0.949878652648.issue6765@psf.upfronthosting.co.za>
2009年08月23日 15:22:51	mark.dickinson	link	issue6765 messages
2009年08月23日 15:22:50	mark.dickinson	create

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