#26 Hospital gives up without warning

closed
nobody
5
2009-03-18
2002-03-26
No

Behavior:

(C1) limit(exp(-1/x)/x^5,x,0,PLUS);

(D1)                                  0
(C2) limit(exp(-1/x)/x^6,x,0,PLUS);

- 1/x
                                        %E
(D2)                           limit   -------
                                x -> 0+    6
                                          x
Explanation (Richard Fateman):

lhospitallim is set to 5. Yes it is arbitrary, but you
can change it.

Expected behavior:

Wouldn't it be nicer if there was some
warning message telling us "I  stopped, but by
changing this variable you could maybe get me to
evaluate the  limit in full"...? This gives the wrong
impression... like "oh! Maxima can't solve that!".

Further comments (Richard Fateman):

I suppose this could be done, but it might also be
the case that after giving up on L'Hopital's rule it
tries something else that might succeed.  The
source code for limit is available.

Further comments (James Amundson):

I agree. It also might be a good idea to increase
the default value.
Computers are bigger and stronger now.

Discussion

  • Robert Dodier

    Robert Dodier - 2006-03-26
    • labels: --> 460522
     
  • Robert Dodier

    Robert Dodier - 2006-03-26

    Logged In: YES
    user_id=501686

    For the record, same behavior in Maxima 5.9.3.

     
  • Robert Dodier

    Robert Dodier - 2006-06-26
    • labels: 460522 --> Lisp Core - Limit
     
  • Raymond Toy

    Raymond Toy - 2006-11-09

    Logged In: YES
    user_id=28849

    I think we should just increase the default to 8 (just as
    arbitrary as 5) and close this bug.

    Alternatively, we could make L'Hopital check to see if the
    numerator or denominator is a polynomial and change the
    limit appropriately.

     
  • Dieter Kaiser

    Dieter Kaiser - 2009-01-01

    I can not read all of this bug report (a lot of unreadable ? chars in the text) but the examples seems to be:

    (%i26) limit(exp(-1/x)/x^5,x,0,plus);
    (%o26) 0
    (%i27) limit(exp(-1/x)/x^6,x,0,plus);
    (%o27) 0

    Both limits work and seems to be right. The bug has gone.

    I have set this bug report to pending.

    Dieter Kaiser

     
  • Dieter Kaiser

    Dieter Kaiser - 2009-01-01
    • status: open --> pending
     
  • SourceForge Robot

    This Tracker item was closed automatically by the system. It was
    previously set to a Pending status, and the original submitter
    did not respond within 14 days (the time period specified by
    the administrator of this Tracker).

     
  • SourceForge Robot

    • status: pending --> closed
     

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