string-variable-Set-snarl
- To: mathgroup at smc.vnet.net
- Subject: [mg22491] string-variable-Set-snarl
- From: James Fuite and Tania Nordli <jfuite at UAlberta.ca>
- Date: Sun, 5 Mar 2000 00:24:27 -0500 (EST)
- Organization: University of Alberta, Edmonton, Canada
- Sender: owner-wri-mathgroup at wolfram.com
Dear Advanced Mathematica Users, The following is a short and perhaps trivial problem that has caused me some frustration. I cannot write a program that allows me to change the value of any given variable if given the name of the variable as a string. What follows is an equivalent situation. Let In[3]= {cow = Random[], emu = Random[], ant = Random[]} Out[3]= {0.2, 0.3, 0.4} . . . . some selection process . . . . In[25]= animalname Out[25]= cow In[25]= Head[animalname] Out[25]= String Given a string, here "cow", corresponding to a variable, here cow, I cannot clear or set a value for the variable itself. Of course I cannot use Clear[cow] or cow = 2 because I do not know which variable will be chosen, as represented by the variable animalname. My lame attempts such as Clear[animalname] or ToExpression[animalname] = 2 only fail to affect cow - it seems that I am caught trying to work on the wrong side of the equals sign (Set)! My goal would be a line such as: In[28]= ToExpression[animalname] Out[28]= 2 which I think would imply that cow = 2 and has thus been affected. Who can guide me from line 25 to line 28? What are the general considerations? Sincerely, James J. Fuite.
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