Re: a[[2]][[3]] = 1 error? why?

*To*: mathgroup at smc.vnet.net*Subject*: [mg8930] Re: [mg8874] a[[2]][[3]] = 1 error? why?*From*: David Withoff <withoff>*Date*: Sat, 4 Oct 1997 22:08:08 -0400*Sender*: owner-wri-mathgroup at wolfram.com

> a=Table[i*j,{i,1,3},{j,1,3}]; > a[[2]][[3]] > > answer : 6 (as it should be) > so why assignment to > a[[2]][[3]] = 3 > doesn't work? This could presumably be made to work, but Part assignments are a rather special type of assignment, and in current versions of Mathematica have only been made to work for a single level of Part, not for nested Part. a[[2]][[3]] is Part[Part[a, 2], 3]. You can make an assignment to the [[2,3]] element of this array using a[[2,3]] instead, as in In[1]:= a=Table[i*j,{i,1,3},{j,1,3}]; In[2]:= a[[2,3]] = 3 Out[2]= 3 In[3]:= a Out[3]= {{1, 2, 3}, {2, 4, 3}, {3, 6, 9}} Dave Withoff Wolfram Research