RE: Iterators

*To*: mathgroup at smc.vnet.net*Subject*: [mg32859] RE: [mg32826] Iterators*From*: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>*Date*: Sat, 16 Feb 2002 04:35:15 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

> -----Original Message----- > From: Juan [SMTP:erfa11 at hotmail.com] To: mathgroup at smc.vnet.net > Sent: Thursday, February 14, 2002 7:44 AM > To: mathgroup at smc.vnet.net > Subject: [mg32826] Iterators > > Hi, > If I write: > > y = Table[Part[w,p[i]],{i,2}], then I get a message saying thet p[i] is > not > a integer. > > How can I avoid that? > > I have to define w[[p[i]]] before I using it; p[i] are iterators and w is > a > list of numbers.Then, at the end,I can write: > Table[{w[[p[1]]],w[[p[2]]},{p[1],a,b},{p[2],p[1],c}] > > This is becouse,the numbers of iterators are enter with the parameters in > the definition of the function, and you don't know that before. > > Thanks > Juan > [Hartmut Wolf] look: In[1]:= w={w1,w2}; p={2,1}; In[3]:= Table[w[[p[[i]]]],{i,1,2}] Out[3]= {w2,w1} In[4]:= w[[p]] (*****) Out[4]= {w2,w1} In[5]:= p=. In[6]:= Table[w[[p[i]]],{p[i],1,2}] Out[6]= {w1,w2} I don't get that message, if p is Unset before. Otherwise it depends, look at your exact message. In[7]:= Table[{w[[p[i]]],w[[p[j]]]},{p[i],1,2},{p[j],1,2}] Out[7]= {{{w1,w1},{w1,w2}},{{w2,w1},{w2,w2}}} You meant something, but I failed to understand. To learn what an iterator is, take this expression to your notebook and click \!\(\* ButtonBox[\(What\ is\ an\ \(\(iterator\)\(\ \)\(?\)\)\), ButtonData:>{ FrontEnd`FileName[ {$RootDirectory, "C:", "Programme", "Wolfram Research", "Mathematica", "4.1", "Documentation", "English", "MainBook"}, "1_05.nb", CharacterEncoding -> "WindowsANSI"], "4.15"}, ButtonStyle->"Hyperlink"]\) Perhaps you need to adapt before "Programme" --> "Program Files", "4.1" --> ?.?, "English" --> ?