Hello. summation(exp(a*x), (x, 1.2, 1.5)) = 0 because a summation with an empty set of indices k is zero by convention. This allows to say that summation over disjoint set A and B is the summation over their union.
Maybe sympy should avoid the use of non integers for the lower and upper bounds. *Christophe BAL* *Enseignant de mathématiques en Lycée **et développeur Python amateur* *---* *French math teacher in a "Lycée" **and **Python **amateur developer* 2015-02-03 9:01 GMT+01:00 Gaurav Dhingra <axyd0...@gmail.com>: > Hi, > I want to know about the "summation" function used in sympy. > > The code should be according to the documentation but for summation, As > @asmeurer had mentioned earlier to me that- "he is not sure regarding the > summation function. That what sympy should be doing with it." > https://groups.google.com/forum/#!topic/sympy/z9mZH10UuY0 > > Right now the documentation does not match with the way summation is done > right now. > > I guess we have choices for implementing the summation function(which i am > noticing are the same as Aaron mentioned in issue #5822 > https://github.com/sympy/sympy/issues/5822) > > 1. Following the way as the documentation says "taking > all integer values from ``start`` through ``end``". > which implies summation like > summation(exp(a*x), (x, 1.2, 1.5)) would result in a value of zero. > (since no integer value is included between 1.2 and 1.5) > I think this would not be the best way to go. As the this would result > in many function summation to result in a value even if the summation > should not exist. > > 2. Following the way sympy is going right now i.e evaluate the the > summation for general expression and than substituting the value of lower > and upper limit. (I don't think it would be a good way to go.) > > 3. Following the way the Wolfram Alpha is doing i.e evaluating making the > lower limit not to be a fraction for evaluating the summation. > > I would like to work on the issue #5822 . > > On Friday, January 23, 2015 at 8:36:18 AM UTC+5:30, Aaron Meurer wrote: >> >> See https://github.com/sympy/sympy/issues/5822 for a discussion on this. >> I'm not sure what convention SymPy should take, but the documentation ought >> to match it. >> >> Aaron Meurer >> >> On Thu, Jan 22, 2015 at 7:56 PM, Gaurav Dhingra <axyd...@gmail.com> >> wrote: >> >>> Hi all >>> >>> I ran the following the following code >>> >>> In[10]: simplify(summation((k), (k, 2, 4.7))) == simplify(summation((k), >>> (k, 2, 4.4))) >>> Out[10]: False >>> >>> I read the documentation of summation function, so according to it the >>> summation includes all the integer values from start to end. But does not >>> seem to follow it. >>> >>> Is this a bug. ? >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "sympy" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to sympy+un...@googlegroups.com. >>> To post to this group, send email to sy...@googlegroups.com. >>> Visit this group at http://groups.google.com/group/sympy. >>> To view this discussion on the web visit https://groups.google.com/d/ >>> msgid/sympy/697cda0a-62db-411e-bf10-a9d601bbcb69%40googlegroups.com >>> <https://groups.google.com/d/msgid/sympy/697cda0a-62db-411e-bf10-a9d601bbcb69%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > Visit this group at http://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/b6924d03-fbbf-4c63-ad87-92a9ac5e0c12%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/b6924d03-fbbf-4c63-ad87-92a9ac5e0c12%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAAb4jG%3DdXGr9XydO5L3qDPu4YsQfgvsde9xQ%2BHXuKYQ743aTaQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
