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. >> 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.
