samer@38: Think about algebra of function handles - scanner_add_plotter etc
samer@12: are special cases function combinators. What is the most general language
samer@12: for function algebra? Is it the arrow algebra restricted to functional arrows?
samer@12: 
samer@12: 
samer@12: Function combinators
samer@12: 	composition :        f*g(x) = f(g(x))
samer@12: 	parallel composition f+g(x,y)=f(x),g(y)
samer@12: 
samer@12: Function types
samer@12: 	state transformers: S->S
samer@12: 	scanner:            Y,X->Y
samer@12: 	folder:             X,S->S
samer@12: 	accum:              Y,S->X,S
samer@12: 
samer@13: Current special cases:
samer@13: 	scanner_add_plotter
samer@13: 	decorate
samer@13: 
samer@12: Also what about actions? (Function with side-effects or dependence on global state)