Date: Jan 21, 2013 12:07 AM
Author: yehuda ben-shimol
Subject: Re: problem with append


There are some errors here
1. The function name is AppendTo (with capital T) - Mathematica is case
sensitive
2. Even this would not help, since r={} in the body of AppendTo refers to
the return value of the assignment rather than to rr
Combining 1 and 2 above results with the immediate correction

rr = {};
For[a = 2, a < 6, a++, For[b = 2, b < 6, b++, AppendTo[rr, a^b]]]
rr


But any decent Mathematica programmer is aware of how inefficient Append,
AppendTo, Prepend, PrependTo and Insert are

You have many other ways, which are more efficient. Note that Do and For
return Null, and what you do is adopting the concept of side effects to
generate lists - a highly inefficient way in Mathematica

Read the documentation on

Table, Array, Flatten

to enhance your programming in Mathematica

yehuda


On Sun, Jan 20, 2013 at 8:21 AM, Paolo cachecho <paolocach@gmail.com> wrote:

> hello i am new to mathmatica.i have the following problem if anyone could
> help.
>
> For[a = 2, a < 6, a++,
>         For[b = 2, b < 6, b++,
>   Appendto[rr = {}, a^b]]]
> rr
>
> but rr remains empty. how can i solve this
> thank you
>
>