changing parts of a list of lists

*To*: mathgroup at smc.vnet.net*Subject*: [mg52565] changing parts of a list of lists*From*: Dan Drake <drake at math.umn.edu>*Date*: Thu, 2 Dec 2004 02:21:19 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

I'm working with a list of lists, such as {{1,2}, {3}, {4,5,6}}, and I want to go through and make changes to each sublist, but I get the error message "Set::setps: {{0,0,0},{0},{0}} in assignment of part is not a symbol." I don't quite understand what's going on. Here's a toy example that shows the error: f[x:{__List}] := For[i=1, i <= Length[x], i++, x[[i]] = {1, 2, 3}] If I wrap it in a Module, I can get it to work, but the "y=x" seems redundant: g[x:{__List}] := Module[{y=x}, For[i=1, i <= Length[y], i++, y[[i]] = {1, 2, 3}]; y] f[{{a},{b}}] fails, but g[{{a},{b}}] works. It seems like the function f should work. What's going on? Thanks, Dan -- --- Dan Drake <drake at math.umn.edu> University of Minnesota ----- http://www.math.umn.edu/~drake School of Mathematics -------

**Follow-Ups**:**Re: changing parts of a list of lists***From:*DrBob <drbob@bigfoot.com>