title: loop through sections of an array
body: <p>Was looking to see if i can get a bit of help with a  problem. So i am currently trying to loop through sections of a 2d array and unsure how to do it.</p>
  
  <p>essentially I’m going to have an array 4x4 or 9x9 or 25x25, and i need to be able to iterate over blocks and check for duplicates. </p>
  
  <p>for example 4x4, i would iterate over 4 2x2 arrays.
  the 9x9 would be 9 3x3 arrays etc.</p>
  
  <p>been trying for a while but have had no luck 
  i have tried this </p>
  
  <p>any help would be great,
  cheers</p>