declaring
  ((a)is a {x,y})
means that
  (get(a))is(composition{x:((a).x),y:((a).y)}) //(get(a)) composes a from its subparts
  (set(a))is(decomposition{x:((a).x),y:((a).y)}) //(set(a)) decomposes a to its subparts

// Use of that


interaction
  (angle of point(a))
with
  ((a) is a {x,y})
is
  (atan2((a).y)((a).x))








interaction
  (testotest(a:{x:Number,y:Number}in)):Number out
is
  ((a).x)
with


  IMPLICITELY we have:
  interaction ((a).x):Number out
  interaction ((a).y):Number out
  interaction
    (a):{x:Number,y:Number}out
  is
    ({x:((a).x),y:((a).y)})










// Other approach ?
interaction
  ((a:{x:<t1>,y:<t2>}in).x):<t1>out
is
  (local of ((a).x))




interaction
  ((a:{x:<t1>,y:<t2>}in).y):<t2>out
is
  (local of ((a).y))




interaction
  (a:{x:<t1>,y:<t2>}):out
is
  ({x:((a).x),y:((a).y)})