In this thread jcl indicates that price(0) is from the bar just closed.

This raises another question though, when writing a trade management function, that will be executed on ticks in a new bar forming, is there a difference between price() and price(0)?

This was easier to get my head around in metatrader where the scripts ran on each tick and the last completed bar was 1 and anything in the current bar was 0.

Zorro may function like metatrader in the functions that execute at a tick level, but normally the scripts execute immediately after a barperiod closes and I suppose theoretically before anything happens in the new barperiod that would need reference to.