utilities.py 文件源码

def getrule():
    """
    Using pyparsing, get rule out of a string.
    """
    arrow = pp.Literal("==>")
    buff = pp.Word(pp.alphas, "".join([pp.alphanums, "_"]))
    special_valueLHS = pp.oneOf([x for x in _LHSCONVENTIONS.keys()])
    end_buffer = pp.Literal(">")
    special_valueRHS = pp.oneOf([x for x in _RHSCONVENTIONS.keys()])
    chunk = getchunk()
    rule_reader = pp.Group(pp.OneOrMore(pp.Group(special_valueLHS + buff + end_buffer + pp.Group(pp.Optional(chunk))))) + arrow + pp.Group(pp.OneOrMore(pp.Group(special_valueRHS + buff + end_buffer + pp.Group(pp.Optional(chunk)))))
    return rule_reader