On 2013-08-21, Robert Bradshaw <[email protected]> wrote: > On Mon, Aug 19, 2013 at 6:30 PM, Dima Pasechnik <[email protected]> wrote: >> On 2013-08-19, Vincent Knight <[email protected]> wrote: >>> --001a1133aa8653f2ed04e4510b09 >>> Content-Type: text/plain; charset=ISO-8859-1 >>> >>> Thanks for the answer kcrisman but I'm afraid I'm still not sure I >>> understand. >>> >>> If by 'unsigned infinity' you mean that Sage is returning positive infinity >>> (but assuming that there is no need to return the '+') then I agree but I >>> also still don't think that this is the required behaviour right? The >>> undirected limit should is not defined (so Sage should return that the >>> 'undefined') and given the help file, the output is a bit confusing... If >>> I'm missing something please do forgive me :) >> >> IMHO "unsigned infinity" simply means NaN (Not a Number). >> Correct me if I'm wrong here. > > No, the unsigned infinity is the infinity in the real projective line, > and is indeed the limit here. It comes up more naturally, of course, > in other areas like doing complex analysis on the Riemann sphere.
Interesting! Is it documented? > >>> On 19 August 2013 19:17, kcrisman <[email protected]> wrote: >>> >>>> >>>> >>>> On Monday, August 19, 2013 1:55:04 PM UTC-4, Vince wrote: >>>>> >>>>> When computing the limit of a function I don't quite seem to be getting >>>>> the behaviour that I expected. >>>>> >>>>> --- >>>>> sage: f(x) = 1 / x >>>>> sage: print f.limit(x=0) >>>>> sage: print f.limit(x=0, dir='minus') >>>>> --- >>>>> >>>>> The first limit returns infinity, but I would expect it to return that >>>>> the limit is not defined. >>>>> >>>> >>>> I think we have an unsigned infinity and a signed infinity. It should >>>> return the former, from Maxima. >>>> >>>> >>>> >>>> >>>>> The second (directional) limit confirms this (it returns -infinity). I >>>>> was assuming that the default 'direction' for a limit is None and that a >>>>> two directional limit would be computed (which in this case does not >>>>> exist). Here's some of the help file that shows why I am perhaps confused: >>>>> >>>>> --- >>>>> INPUT: >>>>> >>>>> - ``dir`` - (default: None); dir may have the value >>>>> 'plus' (or '+' or 'right') for a limit from above, >>>>> 'minus' (or '-' or 'left') for a limit from below, or may be omitted >>>>> (implying a two-sided limit is to be computed). >>>>> --- >>>>> >>>>> If anyone could clarify this I'd appreciate it. >>>>> >>>>> Vince >>>>> >>>> -- >>>> You received this message because you are subscribed to the Google Groups >>>> "sage-support" group. >>>> To unsubscribe from this group and stop receiving emails from it, send an >>>> email to [email protected]. >>>> To post to this group, send email to [email protected]. >>>> Visit this group at http://groups.google.com/group/sage-support. >>>> For more options, visit https://groups.google.com/groups/opt_out. >>>> >>> >>> >>> >>> -- >>> Dr Vincent Knight >>> Cardiff School of Mathematics >>> Senghennydd Road, >>> Cardiff >>> CF24 4AG >>> (+44) 29 2087 5548 >>> www.vincent-knight.com >>> +Vincent Knight >>> @drvinceknight >>> Skype: drvinceknight >>> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sage-support" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/sage-support. >> For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/groups/opt_out.
