obj_scm.js

function make_object(_super, _recvs_) {
  
  var _recvs = Object.assign(
    { lookup: function(s, al) { return _lookup(al[0]); },
      super: function(s, al) { return _call(_super('lookup', [al[0]]), al.slice(1)); }}, _recvs_);
  
  var _lookup = function(n) {
    if (n in _recvs) { return _recvs[n]; }
    else if (_super != undefined) { return _super('lookup', [n]);}
    else { throw 'InvalidMessage'; }}
  
  var _self = function(n, al) { return _call(_lookup(n), al);}
  var _call = function(r, al) { return r(_self, al);}
  
  
  return function(msg, args) { return _call(_lookup(msg), args); }};

function _point(x, y) {
  return make_object(
    undefined,
    { posn: function(s, al) { return [x, y]; },
      eql: function(s, al) {
        var sp = s('posn', []);
        var rp = al[0]('posn', []);
        return ( sp[0] == rp[0] && sp[1] == rp[1]);},
      sum: function(s, al) { return x + y;}})}

function _point3d(x, y, z) {
  return make_object(
    _point(x, y),
    { posn: function(s, al) { return [x, y, z]; },
      sum: function(s, al) { return z + s('super', ['sum']);}})}