Nested for and lists in mathematica

[shakespeare86]

Hello, I'm new using Mathematica and actually can't understand what's the problem in this code

l = {}

For[k = 1, k < 3,
 For[j = 1, j < 3, 
    t1 = RandomInteger[{1, 10}];
    t2 = RandomInteger[{1, 10}];
    t = (t1 + t2)/2;
    j++;
    ]
   l = Append[l, t];
 k++;
 ]

The error I get is

Set::write: Tag Times in Null {} is Protected. >>

I've also tried to use an array or a table in the place of the list l, but the error persist.
It's like if after the nested for, I couldn't append elements to the list or add elements to an array.

Have you any idea to do what I would like to do?

 

[Valkarie]

The problem here is that the variable t is not defined outside of the inner For loop. The value of t is reset to a new random value each time the inner loop is executed, so when you try to use it outside of the loop, it has no value. The easiest way to fix this is to define t before the inner For loop, and then just update its value each time with the new random one.