Re: Transformation rule problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg58057] Re: Transformation rule problem*From*: bghiggins at ucdavis.edu*Date*: Fri, 17 Jun 2005 05:19:13 -0400 (EDT)*References*: <d8rnfg$l4b$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Oliver, try this f //. {a^(x_)*b -> a^(x - 1)*d, a^(x_)*b^(y_) -> a^(x - 1)*b^(y - 1)*d, a*b^(x_) -> b^(x - 1)*d} Cheers, Brian Oliver Buerschaper wrote: > Hi there, > > I'm stuck with a problem concerning transformation rules and was > wondering whether somebody could give me a hint on this. I wouldn't > mind a complete solution either ;-) Here's the problem: > > In a sum like for example > > a^2 b^4 + a^3 b + a^5 + a^5 b > > I'd like to replace every instance of the product (a b) by a different > expression, let's call it d. Thus my result should look like > > d^2 b^2 + a^2 d + a^5 + a^4 d > > This replacement is required to work for arbitrary a and b (especially > when they're functions). I've already tried some simple transformation > rules but they couldn't do the job. > > Cheerio, > Oliver