& fn apply_command {
& 	"Takes a turtle state and a command and calculates a new state."
& 	(state, command) -> 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
& 	}
& }

fn many_args (_, _, x, _) -> x

let fewer_args = many_args (:foo, :bar, _, :baz)

fewer_args(:quux)