& let state = #{:position (0, 0), :heading 0, :pencolor :white}

& let command = (:forward, 10)

& match command with {
& 	(:goto, (x, y)) -> assoc (state, :position, (x, y))
& 	& (:home) -> do state > 
& 	& 	assoc (_, :position, (0, 0)) >
& 	& 	assoc (_, :heading, 0)
& 	& (:clear) -> do state >
& 	& 	assoc (state, :position, (0, 0)) >
& 	& 	assoc (_, :heading, 0)
& 	(:right, turns) -> update (state, :heading, add (_, turns))
& 	(:left, turns) -> update (state, :heading, sub (_, turns))
& 	(:forward, steps) -> {
& 		let #{heading, position, ...} = state
& 		let unit = heading/vector (heading)
& 		let vect = mult (steps, unit)
& 		update (state, :position, add (vect, _))
& 	}
& 	(:back, steps) -> {
& 		let #{heading, position, ...} = state
& 		let unit = heading/vector (heading)
& 		let vect = mult (steps, unit)
& 		update (state, :position, sub (_, vect))
& 	}
& 	& (:penup) -> assoc (state, :pendown?, false)
& 	& (:pendown) -> assoc (state, :pendown?, true)
& 	& (:penwidth, pixels) -> assoc (state, :penwidth, pixels)
& 	& (:pencolor, color) -> assoc (state, :pencolor, color)
& 	& (:setheading, heading) -> assoc (state, :heading, heading)
& 	& (:loadstate, position, heading, visible?, pendown?, penwidth, pencolor) -> #{position, heading, visible?, pendown?, penwidth, pencolor}
& 	& (:show) -> assoc (state, :visible?, true)
& 	& (:hide) -> assoc (state, :visible?, false)
& 	& (:background, _) -> state
& }

box foos = []

repeat 4 {
	update! (foos, append (_, :foo))
}

do foos > unbox > count