arquivo

...

http://pastebin.com/Wesjzs1A

Solution in the article is overly convoluted.

http://www.cs.rit.edu/~ats/books/

It is complicated, but you can take parts from it and built your own system.

http://pastebin.com/uWSs7ca7

We can improve the macro further by removing the unnecessary if statement and the index number:

http://pastebin.com/vPTTYPpe