※ 引述《x0315b100 (飞来飞去)》之铭言： : 在课本上看到了... : 整傻住 : 什麽是BNF阿?? : 全名又是什麽?? : 希望大大能举个例子说明一下@@" : 麻烦了~ Backus-Naur Form – Invented by John Backus to describe Algol 58 – BNF is equivalent to context-free grammars – BNF is a metalanguage used to describe another language – In BNF, abstractions are used to represent classes of syntactic structures--they act like syntactic variables (also called nonterminal symbols ) BNF Fundamentals ‧ Non-terminals: BNF abstractions ‧ Terminals: lexemes and tokens ‧ Grammar: a collection of rules – Examples of BNF rules: <ident_list> → identifier | identifier, <ident_list> <if_stmt> → if <logic_expr> then <stmt> supplement: The example Grammar : <program> → <stmts> <stmts> → <stmt> | <stmt> ; <stmts> <stmt> → <var> = <expr> <var> → a | b | c | d <expr> → <term> + <term> | <term> - <term> <term> → <var> | const For a = b + const it's derivation is: <program> => <stmts> => <stmt> => <var> = <expr> => a = <expr> => a = <term> + <term> => a = <var> + <term> => a = b + <term> => a = b + const Read "Program Language" books for more detail. -- 空中精灵。SkyElf/Stevennick 　　　　　　　要重新在空中飞翔‧遨游全世界　未来正在我的手中　一点一滴的实现 　　　 　　　　　　　 　　 My Blog: http://stevennick.dyndns.org/ 　 　 　　　　　　　My Podcasting: http://podcast.blog.webs-tv.net/skyelf 　____________________________________________________________________________ --

※ 发信站: 批踢踢实业坊(ptt.cc) ◆ From: 219.68.140.151