Problems with Evaluate[Symbol[xxx]]

*To*: mathgroup at smc.vnet.net*Subject*: [mg102759] Problems with Evaluate[Symbol[xxx]]*From*: Keelin <keelinm at gmail.com>*Date*: Wed, 26 Aug 2009 07:44:06 -0400 (EDT)

Hi, I'm trying to use the Evaluate[Symbol[xxx]] syntax but I think I am misunderstanding something as it is not behaving as I expect. Below is an example to illustrate what is unexpected: The questions are: 1) Is there a problem with line 604 - it gives errors, but yet the output in the end is correct 2) Why are the output of abc and the output of Evaluate[Symbol [myListIdentifier]] not regarded as equal even though they appear identical (See line 608) 3) Why can I append correctly using the reference name abc, but not using the Evaluate[Symbol[myListIdentifier]] name? This is what I really want to do in the end - append to a list which has a dynamically assigned variable name. Thanks!! In[602]:= (*Make an identifier string to hold some data*) myListIdentifier = "abc" Out[602]= "abc" In[603]:= (*here's the data*) myList = {{7, 8}} Out[603]= {{7, 8}} In[604]:= (*Now put the data into a variable with name abc*) Evaluate[Symbol[myListIdentifier]] = myList During evaluation of In[604]:= Set::setraw: Cannot assign to raw \ object 7. >> During evaluation of In[604]:= Set::setraw: Cannot assign to raw \ object 8. >> Out[604]= {{7, 8}} In[605]:= (*Check abc holds the correct data*) abc Out[605]= {{7, 8}} In[606]:= (*Check the data can also be accessed using the \ myListIdentifier*) In[607]:= Evaluate[Symbol[myListIdentifier]] Out[607]= {{7, 8}} In[608]:= (*But apparently the two items are not equal... why??*) abc == Evaluate[Symbol[listIdentifier]] Out[608]= False In[609]:= (*Even worse, I can append using the reference abc, but not \ using the myListIdentifier*) Append[abc, {3}] Out[609]= {{7, 8}, {3}} In[610]:= Append[Evaluate[Symbol[listIdentifier]], {3}] Out[610]= {{3}}