public void addLoop(ArrayComprehensionLoop acl){
  assertNotNull(acl);
  loops.add(acl);
  acl.setParent(this);
}

public void addLoop ( ArrayComprehensionLoop acl ) { assertNotNull ( acl ) ; loops . add ( acl ) ; acl . setParent ( this ) ; }
adds a child loop node , and sets its parent to this node .
