Re: newbie question about inserting values

*To*: mathgroup at smc.vnet.net*Subject*: [mg95526] Re: newbie question about inserting values*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Tue, 20 Jan 2009 06:58:14 -0500 (EST)*Organization*: Uni Leipzig*References*: <gl4a2o$gco$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, try test[4] /. test[n_] /; n > 0 :> n*test[(n - 1)] and test[4] //. test[n_] /; n > 0 :> n*test[(n - 1)] Regards Jens SaintPatrick wrote: > Hello all, > > Okay, take a look at this snippet from the book "Mathematica > Navigator." > '***************************** > p = x + Sin[y]; > > Consider the following example > > p/. x->y/.y->a > > y+ Sin[a] > > At each part of p, the rules are applied only once. Write then the > following: > > p/.x->y/.y->a > > a+Sin[a] > > First x is replaced with y, and then y is replaced with a. Mathematica > also has the command ReplaceRepeated, which is formed by //.. It > applies the rules until the result no longer changes: > > p//.{x->y,y->a} > > a+Sin[a] > ********************************** > > I'm having trouble understanding what the exact difference internally > is between > > p/.x->y/.y->a > > and > > p//.{x->y,y->a} > > I'd appreciate some enlightenment. Thanks. > > > Patrick >