(self, p)
list : list LT freq
list : list LT freq
list : list LT freq
def p_list_lt(self, p):
        'list : list LT freq'
        p[0] = p[1][p[1] < p[3]]
def p_list_lt ( self , p ) : p [ 0 ] = p [ 1 ] [ p [ 1 ] < p [ 3 ] ]