how can it be so much faster? its written in C or something? its built in the language somehow i guess, its not possible to recreate for me by writing a def?
It is probably written in C and does not check its args every time it is called. Basically, every time you call 'is, '<, '+, or any other primitive operation, it checks whether its arguments are numbers, then performs the operation. All these checks are useless since, within the body of your function, you know the type of your args are numbers, but you cannot avoid them anyway. Optimization will come, later :)
