Re: D under Sum
- To: mathgroup at smc.vnet.net
- Subject: [mg128392] [mg128392] Re: D under Sum
- From: Nicolas Venuti <nicolas at virtualdynamics.fr>
- Date: Fri, 12 Oct 2012 00:00:47 -0400 (EDT)
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Thank you Bob Unfortunatly it does not work for : D[p i + holdSum[p*i, {i, 1, n}], p] or any expression that include (recursively) holdSum Le 11 oct. 2012 =E0 14:26, Bob Hanlon a =E9crit : > It is recommended that user-defined functions always start with a > lower case letter to avoid any potential naming conflicts with current > or future built-in functions. > > Use UpValues > > holdSum /: D[ > holdSum[expr_, iter_?VectorQ], > x_Symbol] := > holdSum[D[expr, x], iter]; > > holdSum /: ReleaseHold[holdSum[arg__]] := > Sum[arg]; > > D[holdSum[p*i, {i, 1, n}], p] > > holdSum[i, {i, 1, n}] > > % // ReleaseHold > > (1/2)*n*(1 + n) > > > Bob Hanlon > > > On Thu, Oct 11, 2012 at 2:09 AM, Nicolas Venuti > <nicolas at virtualdynamics.fr> wrote: >> 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 >>
- References:
- D under Sum
- From: Nicolas Venuti <nicolas@virtualdynamics.fr>
- D under Sum