[StefanKarpinski]

Perhaps the best way to understand what makes Julia fast is to watch these two videos about Python and R and what makes them so hard to optimize:

https://www.youtube.com/watch?v=qCGofLIzX6g

https://www.youtube.com/watch?v=HStF1RJOyxI

Take everything mentioned in these videos that make Python and R really hard to optimize and don't do those things :D