D under Sum

*To*: mathgroup at smc.vnet.net*Subject*: [mg128382] D under Sum*From*: Nicolas Venuti <nicolas at virtualdynamics.fr>*Date*: Thu, 11 Oct 2012 02:09:47 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Hello I want the derivation D to be applied under the Sum sign, I have a function HoldSum that do not evaluate but is similar to Sum in form In[3]:= D[HoldSum[p*i, {i, 1, n}], p] I get the output : Out[3]=i*HoldSum^(1, {0, 0, 0})[i p, {i, 1, n}] but I would want that D be applied under the Sum sign like done by hand here : In[5]:= HoldSum[D[p i, i], {i, 1, n}] Out[5]= HoldSum[p, {i, 1, n}] Obviously I want D to work for any expression containing HoldSum (even on nested HoldSum expression) Does anybody knows how to do that ? Best regards Nicolas

**Follow-Ups**:**Re: D under Sum***From:*Bob Hanlon <hanlonr357@gmail.com>