List manipulation question

*To*: mathgroup at smc.vnet.net*Subject*: [mg15852] List manipulation question*From*: Maarten.vanderBurgt at icos.be*Date*: Fri, 12 Feb 1999 18:40:13 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Dear all, In the following piece of code I define a function Swap23 which is ment to swap elements 2 and 3 in a list. Executing the function on a simple list I get an error. Why do I get this error? Why do I not get this error when I execute the commnad from Swap23 "by hand" as is shown in In[4]? Thanks for any help Maarten van der Burgt Icos Vision Systems Leuven Belgium In[1]:=Swap23[L_List]:=Module [ {temp}, temp = L[[2]]; L[[2]]=L[[3]]; L[[3]] =temp; L ] In[2]:= mylist = {1,2,3}; In[3]:= Swap23[mylist] Set::"setps": "\!\({1, 2, 3}\) in assignment of part is not a symbol." Set::"setps": "\!\({1, 2, 3}\) in assignment of part is not a symbol." Out[3]= {1,2,3} In[4]:= temp = mylist[[2]]; mylist[[2]]=mylist[[3]]; mylist[[3]] =temp; mylist Out[4]= {1,3,2}

**Follow-Ups**:**Re: List manipulation question***From:*Jurgen Tischer <jtischer@col2.telecom.com.co>