RE: Structure modification and related questions

*To*: mathgroup at smc.vnet.net*Subject*: [mg13893] RE: [mg13857] Structure modification and related questions*From*: Daniel CLEMENT <dclement at mail.cpod.fr>*Date*: Sun, 6 Sep 1998 02:55:30 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Hello, > ----- Original Message ----- > From: Roberto Moriyon [SMTP:Roberto.Moriyon at ii.uam.es] To: mathgroup at smc.vnet.net > Sent: Wednesday, September 02, 1998, 7:30:54 > To: mathgroup at smc.vnet.net > Subject: [mg13857] Structure modification and related questions > [...] > > x=Table[i, {i,10000}] > > Q.1) Can I modify x[[3]], let's say, without having to create another > list of 10000 elements? (the obvious thing for me to try, x[[3]]=0, > does not work). > According to me this is the role of the ReplacePart function: x=ReplacePart[x,0,3] [...] > > Q.3) Related to Q.1&2, is it possible in Mathematica that two structures > (or lists, for that sake) have some parts in common? What I mean by > this is that, for example, I would like to have the variable x equal to > the second element of {1,{2,3},4}, so that in case the 3 is changed by > a 5 in one of them, it is also changed in the other one. > It is enough to use SetDelayed (:=): list1={1,{2,3},4} x:=list1[[2]] list1=ReplacePart[list1,5,{2,2}] (the 3 is at place {2,2} in list1) x is now {2,5} > > ----- End Of Original Message ----- regards, Daniel CLEMENT