请问这是用到了什么语法？

Question

代码如下：

replacement_field ::=  "{" [field_name] ["!" conversion] [":" format_spec] "}"
field_name        ::=  arg_name ("." attribute_name | "[" element_index "]")*
arg_name          ::=  [identifier | integer]
attribute_name    ::=  identifier
element_index     ::=  integer | index_string
index_string      ::=   +
conversion        ::=  "r" | "s" | "a"
format_spec       ::=

原文链接

请问上面代码中的{},[],()分别代表了什么意思？这是什么语法？谢谢！

Answer 1

你这个是BNF范式吧 描述语法结构的
http://baike.baidu.com/link?url=tE2TKLRxCr532hID3aCL5Z1arf6gWy4pSPhNNRUPxiusGdpnnfW3gfd9xmhU6b4fdB_mByjmx3we5WvJhYSSi0T85KJLKu2N6D5NcPw0U_W_fS6a39yuMEDWSO_tqJWbIhDPnfgxgNHoKAsfRj6NaGMp46baKrsRsLNTixa16q7