COM SCI 131 Lecture 3:
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S a" chars b" nechars c" chars a" chars b" chars c" chars chars chars. We are focusing only on a small grammar in the message_id. Msg-id = < word *( . word ) @ atom *( . atom ) > . The above uses ebnf, which is just extended version of bnf, like the grammar used in homework 1 and 2. Example ebnf rule could be used to generate all message-id of emails, every email will be represented by a unique message-id: The above grammar will cause trouble, has a breakpoint, edge case. We can add \ in front of a null byte (000 in ctls), which will cause stremp in the c language be confused. Can write a regular expression to identify any message-id built using this grammar. Tail-recursive grammar can be turned into regular expression. i. e if in this grammar, every end of the rule is another non-terminal.
