Re: Simplify Expressions with Non commutative multiplication

*To*: mathgroup at smc.vnet.net*Subject*: [mg60330] Re: Simplify Expressions with Non commutative multiplication*From*: Robert Schoefbeck <schoefbeck at hep.itp.tuwien.ac.at>*Date*: Tue, 13 Sep 2005 06:07:11 -0400 (EDT)*References*: <dfrgic$fpu$1@smc.vnet.net> <dfudi2$1m1$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

thanks for the suggestion, but the form of the cancellation in my previous message was just a special case, the general form being myDot[P1___,M1,inv[M1+M2+...]P2___] + myDot[P1___,M2,inv[M1+M2+...]P2___] + myDot[P1___,M3,inv[M1+M2+...]P2___] + ... should be transformed to myDot[P1,P2]. i had thought about programming a mySimplify working on luists but the combinatorics is quite messy and i wanted mathematica to help me in the first place, not being an obstacle. i do think that my demand is very close to what mathematica can actually do, there should be a tiny trick to cast simplify on noncommutative expressions. robert schoefbeck David Bailey wrote: > Hello, > > One problem with patterns of the form a___,something,b___ (or even more > complicated variants) is that they can work, but involve a combinatorial > explosion of possiblities - so things get hopelessly too slow when you > scale the code up to work on real problems. > > A more efficient approach might be to treat the contents of your myDot > as a list and process it from left to right either recursively or even > indexing the terms explicitly using [[k]]. > > David Bailey > http://www.dbaileyconsultancy.co.uk >