Source code in the jq programming language

def Point(x;y): {"type": "Point", "x": x, "y": y};
def Point(x): Point(x;0);
def Point: Point(0);

def Circle(x;y;r): {"type": "Circle", "x": x, "y": y, "r": r};
def Circle(x;y): Circle(x;y;0);
def Circle(x): Circle(x;0);
def Circle: Circle(0);

def print:
  if  .type == "Circle" then "\(.type)(\(.x); \(.y); \(.r))"
  elif .type == "Point" then "\(.type)(\(.x); \(.y))"
  else empty
  end;

# keyname should be (or evaluate to) a string
def set(keyname; value): 
  if type == "object" and .type and has(keyname) then .[keyname] = value 
  else error("set: invalid type: \(.)")
  end;

Circle(0;1;2) | .x = 1 | print