Re: Naming pieces of patterns
- To: mathgroup at smc.vnet.net
- Subject: [mg29830] Re: [mg29816] Naming pieces of patterns
- From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
- Date: Fri, 13 Jul 2001 04:19:13 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
"Simple" it isn't but: 1. In[5]:= {-(I/(2*a)), I/(2*a)} /. Times[Complex[0,Rational[s_,2]],Power[a,-1]]->s*A Out[5]= {-A,A} 2. In[6]:= {a + b, -(a + b)} /. (s_.)*a + (s_.)*b -> s*e Out[6]= {e,-e} 3. In[7]:= {-Sqrt[a + b], 1/Sqrt[a + b]} /. (a + b)^(Rational[s_, 2]) -> e^s Out[7]= 1 {-e, -} e 4. In[8]:= {I, 2 I, -I} /.Complex[0,a_]->a*J Out[8]= {J,2 J,-J} -- Andrzej Kozlowski Toyama International University JAPAN http://platon.c.u-tokyo.ac.jp/andrzej/ http://sigma.tuins.ac.jp/~andrzej/ on 01.7.12 3:52 PM, Cyril Fischer at fischerc at itam.cas.cz wrote: > How can I as simply as possible use "substitutions" > 1. > -(I/(2 a)) /. I/(2 a) -> A > does not work, while > (I/(2 a)) /. I/(2 a) -> A > works well > > 2. > {(a + b), -(a + b)}/. a + b -> e > gives > {e, -a - b} > instead of {e,-e} > > 3. > {-Sqrt[a + b], 1/Sqrt[a + b]} /. Sqrt[a + b] -> e > gives > {-e,1/Sqrt[a + b]} > > 4. > {I, 2 I, -I} /. I -> J > gives > {J, 2 \[ImaginaryI], -\[ImaginaryI]} > > I know _why_ these cases do not work, but I would like to know, if there > is a possibilty to use a common pattern rule to substitute all > occurences of an expression. > > Thank you, > Cyril Fischer > > >