Re: algebraic substitution rules
- To: mathgroup at smc.vnet.net
- Subject: [mg30736] Re: algebraic substitution rules
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Sun, 9 Sep 2001 03:26:25 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <9ncfq6$pt5$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi, the onlyne help say: ReplaceAll looks at each part of expr, tries all the rules on it, and then goes on to the next part of expr. The first rule that applies to a particular part is used; ******************************************************** no further rules are tried on that part, *************************************** or on any of its subparts since a_ match to the full expression the rule a_->Expand[a] is used and no future rules are tried on that part. You mean 1 + x^2 + x^3 + x^4 /. {x^2 -> 1 + y, x^3 -> y(1 + y), x^4 -> (1 + y)^2} /. a_ :> Expand[a] Regards Jens Cattiaux Isabelle wrote: > > > Hi, > > Could someone tell me why the first substitution rule > works and the second doesn't > > In[1]:== > 1+x^2+x^3+x^4 /. {x^2->1+x ,x^3->x(1+x) ,x^4->(1+x)^2} > > Out[1]== > 2 + x + x(1 + x)+ (1 + x)^2 > > In[78]:== > 1+x^2+x^3+x^4 /. {x^2->1+x ,x^3->x(1+x) ,x^4->(1+x)^2,a_->Expand[a]} > > Out[78]== > 1 + x^2 + x^3 + x^4 > > -- > Isabelle Cattiaux-Huillard > Universite de Valenciennes