dependent exp-s at every input. So basically you could say 'a = 1; b = sin(a*math.pi); c=math.sqrt(b)' and later on every time you change 'a' you can also see 'b' and 'c' changing simultaneously
This is cute - amazing how much power comes out of a simple set of rules.
Sounds like something that Hisham might be interested in - he was generalizing spreadsheets