Re: ReplaceAll / sequential replacements versus joint replacement
- To: mathgroup at smc.vnet.net
- Subject: [mg55452] Re: [mg55429] ReplaceAll / sequential replacements versus joint replacement
- From: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>
- Date: Thu, 24 Mar 2005 03:41:51 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
>-----Original Message----- >From: Ronald Wendner [mailto:Ronald.Wendner at uni-graz.at] To: mathgroup at smc.vnet.net >Sent: Wednesday, March 23, 2005 11:35 AM >Subject: [mg55452] [mg55429] ReplaceAll / sequential replacements versus >joint replacement > >Suppose there is an expression e1 which depends, among others, >on variables >a and b. >Replace both a and b by zero: > >e1/.{a->0,b->0} Mathematica gives, say, result1. > >Next, consider > >e2 = e1/.{a->0}; >e2/.{b->0} Mathematica gives, say, result2. > >How can result 1 differ from result 2? > >For my specific problem, I also attach a short Mathematica notebook. >[Contact the author to obtain the notebook - moderator] > >I'd appreciate any help. > >Many thanks, >Ron > > > Ron, see Help: "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." This makes it clear: there *are* differences. For your special problem, publish it (according to the rules of this group). -- Hartmut Wolf