def p_expression_parentheses(p):
    """expression : LPAREN expression_list RPAREN
                  | LFLOOR expression_list RFLOOR
                  | LCEIL expression_list RCEIL
                  | VERT expression_list VERT
                  """
    tokenToFunc = {'\\lceil': 'ceil', '\\lfloor': 'floor', '\\vert': 'abs',
        '(': ''}
    p[0] = '%s(%s)' % (tokenToFunc[p[1]], p[2])
