def p_parameters(p):
 if (len(p) == 3):
  p[0] = []
 else:
  p[0] = p[2]

def p_parameters ( p ) : if ( len ( p ) == 3 ) : p [ 0 ] = [ ] else : p [ 0 ] = p [ 2 ]
parameters : lpar rpar | lpar varargslist rpar .