Summation convention

*To*: mathgroup at christensen.cybernetics.net*Subject*: [mg204] Summation convention*From*: corcoran (Stephen Corcoran) <corcoran%markov.stats at comlab.oxford.ac.uk>*Date*: Sat, 19 Nov 1994 14:50:11 +0000

Dear Mathgroupers, I wonder if you could help me, I need to set up a rule of the following form, rule = {b[a[x_]] -> d[a[y],a[x]] c[a[y]]}, where a[y] must differ from all other indices a[k] used so far. My application involves expressions involving use of the summation convention which I would like to manipulate using Mma. Thus, in "rule" given above, the RHS is interpreted as being summed over the index a[y]. I need to ensure that, in any given complicated expression, that if e = b[a[1]] b[a[2]] and each b[a[j]] (j=1,2) is to be replaced by a term involving summation using the above "rule", that the indices using in each summation are different. One thing I thought of involved incrementing the summation index y in "rule" each time I used it, but this would not work as if I write f = e /. rule "rule" is applied twice before I have a chance to increment y. Any suggestions? (I am actually away for the next week, but I look forward to reading email on my return!), Thanks, Stephen -------------------------------------------------------------------------- Stephen Corcoran, email: corcoran at stats.ox.ac.uk (internet) Dept. of Statistics, corcoran at uk.ac.ox.stats (janet) University of Oxford, 1, South Parks Road phone: (0865) 272879 OXFORD, OX1 3TG fax: (0865) 272595 --------------------------------------------------------------------------