Services & ResourcesWolfram ForumsMathGroup Archive

[Date Index] [Thread Index] [Author Index]

Re: Just another Mathematica "Gotcha"

• To: mathgroup at smc.vnet.net
• Subject: [mg120810] Re: Just another Mathematica "Gotcha"
• From: Joerg Roesgen <biophys.hershey at me.com>
• Date: Wed, 10 Aug 2011 06:50:22 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201108091119.HAA15770@smc.vnet.net>

Of course they are different. Consider

Normal /. {b2 -> 0}
Series[a + (b1 + b2) x, {x, 0, 1}] // %




On Aug 9, 2011, at 7:19 , 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>