Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1998
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1998

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

Search the Archive

list referencing with [[ ]][[ ]]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg13969] list referencing with [[ ]][[ ]]
  • From: tdelling at ews.uiuc.edu (Tim Dellinger)
  • Date: Fri, 11 Sep 1998 15:06:57 -0400
  • Organization: University of Illinois at Urbana-Champaign
  • Sender: owner-wri-mathgroup at wolfram.com

According to "the book" section 1.8.4,

t[[1]][[2]] "is equivalent to" t[[1,2]], "but is clumsier to write"

and that is all that I can find concerning the difference between the
two ways of refering to a list element.

But...

 In[37]:=
 alist = {{1,2},{3,4}}; alist[[2,1]] = 7 ; alist

 Out[37]=
 {{1,2},{7,4}}

So far so good, and yet...

 In[39]:=
 anotherlist = {{1,2},{3,4}}; anotherlist[[2]][[1]] = 7
 Set::"setps": 
    "\!\(anotherlist \\[LeftDoubleBracket] 2 \\[RightDoubleBracket]\) in
\
 assignment of part is not a symbol."
 Out[39]=
 7

What's the problem here?  Is there a difference between the two ways of
referencing list elements that "the book" neglects to mention?


--
--
"Perhaps my most deeply rooted hobby is to understand         Tim
Dellinger
 the mechanisms of simple and familiar                   
tdelling at uiuc.edu
 natural phenomena." Irving Langmuir     
http://www.ews.uiuc.edu/~tdelling


  • Prev by Date: Black-Scholes and exotic options
  • Next by Date: Wolfram Research Grant Programs
  • Previous by thread: Re: Black-Scholes and exotic options
  • Next by thread: Re: list referencing with [[ ]][[ ]]