Re: Just another Mathematica "Gotcha"
- To: mathgroup at smc.vnet.net
- Subject: [mg120781] Re: Just another Mathematica "Gotcha"
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Wed, 10 Aug 2011 06:44:56 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <201108091119.HAA15770@smc.vnet.net>
It's just a question of the order of precedence. If you are not sure, either use brackets: (Series[a + (b1 + b2) x, {x, 0, 1}] /. {b2 -> 0}) // Normal a+b1 x (Series[a + (b1 + b2) x, {x, 0, 1}] // Normal) /. {b2 -> 0} a+b1 x or don't use the Postfix form at all: Normal[Series[a + (b1 + b2) x, {x, 0, 1}] /. {b2 -> 0}] a+b1 x Normal[Series[a + (b1 + b2) x, {x, 0, 1}] // Normal /. {b2 -> 0}] a+b1 x You are obviously exceptionally talented in created your own "Gotchas". Andrzej Kozlowski On 9 Aug 2011, at 13:19, AES wrote: > Seems as if the following two expression should yield the same output > -- seems that way to me anyway -- but they don't. I'll hide the > actual outputs down below so Mathematica gurus (or "ordinary users") > can make their predictions as to which one does what. > > In[1]:= Series[a+(b1+b2)x,{x,0,1}] //Normal /.{b2->0} > > In[2]:= Series[a+(b1+b2)x,{x,0,1}] /.{b2->0} //Normal > > My conclusions: > > 1) By any normal rules of interpretation or ordinary interpretations > of these statements, they both should do the same same thing. > > 2) This is just another Mathematica "Gotcha" -- and not a > particularly forgivable one. > > > > > > > > > > > > > > > > Out[1]= a+(b1+b2) x > > Out[2]= a+b1 x >
- References:
- Just another Mathematica "Gotcha"
- From: AES <siegman@stanford.edu>
- Just another Mathematica "Gotcha"