TCAD.TWO.ParametricManager.prototype._fetchTwoPoints = function(objs) {
  var points = [];
  for (var i = 0; i < objs.length; ++i) {
    if (objs[i]._class == 'TCAD.TWO.EndPoint') {
      points.push(objs[i]);
    } else if (objs[i]._class == 'TCAD.TWO.Segment') {
      points.push(objs[i].a);
      points.push(objs[i].b);
    }
  }
  if (points.length < 2) {
    throw "Illegal Argument. Constraint requires 2 points or 1 line."
  }
  return points;
};

TCAD.TWO.ParametricManager.prototype._fetchArcs = function(objs, min) {
  var arcs = [];
  for (var i = 0; i < objs.length; ++i) {
    if (objs[i]._class == 'TCAD.TWO.Arc') {
      arcs.push(objs[i]);
    }
  }
  if (arcs.length < min) {
    throw "Illegal Argument. Constraint requires ata least " + min + " arcs."
  }
  return arcs;
};

TCAD.TWO.ParametricManager.prototype._fetchPointAndLine = function(objs) {

  var point = null;
  var line = null;

  for (var i = 0; i < objs.length; ++i) {
    if (objs[i]._class == 'TCAD.TWO.EndPoint') {
      point = objs[i];
    } else if (objs[i]._class == 'TCAD.TWO.Segment') {
      line = objs[i];
    }
  }
  if (point == null || line == null) {
    throw "Illegal Argument. Constraint requires point and line."
  }

  return [point, line];
};

TCAD.TWO.ParametricManager.prototype._fetchArcAndLine = function(objs) {

  var arc = null;
  var line = null;

  for (var i = 0; i < objs.length; ++i) {
    if (objs[i]._class == 'TCAD.TWO.Arc') {
      arc = objs[i];
    } else if (objs[i]._class == 'TCAD.TWO.Segment') {
      line = objs[i];
    }
  }
  if (arc == null || line == null) {
    throw "Illegal Argument. Constraint requires arc and line."
  }

  return [arc, line];
};

TCAD.TWO.ParametricManager.prototype._fetchTwoLines = function(objs) {
  var lines = [];
  for (var i = 0; i < objs.length; ++i) {
    if (objs[i]._class == 'TCAD.TWO.Segment') {
      lines.push(objs[i]);
    }
  }
  if (lines.length < 2) {
    throw "Illegal Argument. Constraint requires 2 lines."
  }
  return lines;
};