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BNF    
巴科斯范式

巴科斯范式

{Backus-Naur Form}. Originally Backus Normal Form.

[{Jargon File}]

Backus-Naur Form (TTCN, ...)

BNF: /B·N·F/, n. 1. [techspeak] Acronym for Backus Normal
Form (later retronymed to Backus-Naur
Form because BNF was not in fact a normal form), a metasyntactic
notation used to specify the syntax of programming languages, command sets,
and the like. Widely used for language descriptions but seldom documented
anywhere, so that it must usually be learned by osmosis from other hackers.
Consider this BNF for a U.S. postal address:


 <postal-address> ::= <name-part> <street-address> <zip-part>



 <personal-part> ::= <name> | <initial> "."



 <name-part> ::= <personal-part> <last-name> [<jr-part>] <EOL>

               | <personal-part> <name-part>



 <street-address> ::= [<apt>] <house-num> <street-name> <EOL>



 <zip-part> ::= <town-name> "," <state-code> <ZIP-code> <EOL>

This translates into English as: “A postal-address consists of
a name-part, followed by a street-address part, followed by a zip-code
part. A personal-part consists of either a first name or an initial
followed by a dot. A name-part consists of either: a personal-part
followed by a last name followed by an optional jr-part (Jr., Sr., or
dynastic number) and end-of-line, or a personal part followed by a name
part (this rule illustrates the use of recursion in BNFs, covering the case
of people who use multiple first and middle names and/or initials). A
street address consists of an optional apartment specifier, followed by a
street number, followed by a street name. A zip-part consists of a
town-name, followed by a comma, followed by a state code, followed by a
ZIP-code followed by an end-of-line.” Note that many things (such as
the format of a personal-part, apartment specifier, or ZIP-code) are left
unspecified. These are presumed to be obvious from context or detailed
somewhere nearby. See also parse.


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  • Precedence of operators in BNF grammar - Stack Overflow
    Swapping + and * in the grammar will clearly swap the precedence, but making them right-associative is a separate step, so that's easy
  • BNF范式(巴科斯范式)到底是什么? - 知乎
    最著名的文法描述形式是由Backus定义 Algol60 语言时提出的 Backus-Naur范式 (Backus-Naur Form, BNF)及其扩展形式 EBNF 。BNF能以一种简洁、灵活的方式描述语言的语法。具体内容可参考针对编译原理的书。
  • syntax - Bracket and brace usage in BNF? - Stack Overflow
    @JonathanLeffler I assume the dialect of BNF is the most basic, academic dialect of BNF, since my text only covers BNF and EBNF and doesn't specify any particular dialect of BNF This is why I assumed braces brackets can't be used in "BNF" in this context I believe the parenthesis is a literal, it isn't explicitly stated though –
  • BNF grammar and Operator Associativity - Stack Overflow
    The BNF grammar given seems consistent with the parse tree, and consistent with the claim that "and" is supposed to be left-associative If you want to produce "a and b and c" using this grammar, starting with "Clause", you start this way: Clause; Clause and Phrase
  • BNF vs EBNF vs ABNF: which to choose? - Stack Overflow
    BNF A ::= B C B ::= a | b | c EBNF A ::= (a | b | c) C This is true for many syntax issues that are allowed in an EBNF or ABNF grammar, thanks to syntactic sugar but not with a normal BNF ABNF extends EBNF , allowing you to do more complicated things, like specifying how many occurrence of a symbol can be found together (i e 4*DIGIT )
  • bnf - Tool for generating railroad diagram used on json. org - Stack . . .
    There is an Online Railroad Diagram Generator It creates SVG syntax diagrams, also known as railroad diagrams, from context-free grammars specified in EBNF
  • parsing - How to represent negation in BNF? - Stack Overflow
    Context free grammars are not closed under "difference" or "complements" So while you might decide to add an operator "subtract" to your BNF, the result will not be a context free grammar even if it has a simple way to express it Consequence: people don't allow such operators in BNF grammars used to express context-free grammars
  • How to convert BNF to EBNF - Stack Overflow
    EBNF or Extended Backus-Naur Form is ISO 14977:1996, and is available in PDF from ISO for free * It is not widely used by the computer language standards
  • What are Context-Free Grammars and Backus Naur Form?
    What is the BNF of BNF? i e How do we define a BNF meta-grammar? 2 Context-Free Grammar 30
  • abstract syntax tree - Source + (E)BNF = ast. json - Stack Overflow
    DMS's BNF will handle any context-free grammar using just BNF rules ANTLR4 handles most grammars but has restrictions on what you can write (e g , certain kinds of left recursion are verboten), and requirements for you to add extra disambiguating information where the grammar isn't LL(1) DMS will export XML directly See this example





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