public void addParam(AstNode param){
  assertNotNull(param);
  if (params == null) {
    params=new ArrayList<AstNode>();
  }
  params.add(param);
  param.setParent(this);
}

public void addParam ( AstNode param ) { assertNotNull ( param ) ; if ( params == null ) { params = new ArrayList < AstNode > ( ) ; } params . add ( param ) ; param . setParent ( this ) ; }
adds a parameter to the function parameter list . sets the parent of the param node to this node .
