Re: Just another Mathematica "Gotcha"
- To: mathgroup at smc.vnet.net
- Subject: [mg120833] Re: Just another Mathematica "Gotcha"
- From: David Bailey <dave at removedbailey.co.uk>
- Date: Fri, 12 Aug 2011 05:05:02 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <j2069b$6vn$1@smc.vnet.net>
On 11/08/2011 10:10, Glenn Carlson wrote: > Yes, I think it's a matter of precedence. For example, > > In[1]:= Normal /. b2 -> 0 > Series[a + (b1 + b2) x, {x, 0, 1}] // % > > Out[1]= Normal > Out[2]= a + (b1 + b2) x > > At my level of proficiency with Mathematica, I shy away from stringing together too many operations. I prefer smaller, more manageable portions. > > It took my brain some time before it allowed me to see [1] as a legitimate operation. Is [1] just a curiosity? Or is there a situation that would call for such usage? > > Thanks and regards, > Glenn > I would not describe this as a total curiosity. 1) There are plenty of situations in which you might want to apply a substitution whether or not it will actually 'fire'. You certainly would not to have to write code to test if an expression contained b2 before applying a replacement operation to remove b2! 2) Creating a head of an expression that is, itself subject to evaluation isn't that unusual. A simple use is to create a synonym of a function: In[673]:= sine=Sin Out[673]= Sin In[674]:= sine[0.2] Out[674]= 0.198669 David Bailey http://www.dbaileyconsultancy.co.uk