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BNF
nonterm
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BNF-group
optional
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4.6 BNF Grammars

 (require scribble/bnf) package: scribble-lib
The scribble/bnf library provides utilities for typesetting grammars.

For example,

  @(let ([open @litchar{(}]

         [close @litchar{)}])

     @BNF[(list @nonterm{expr}

                @nonterm{id}

                @BNF-seq[open @kleeneplus[@nonterm{expr}] close]

                @BNF-seq[open @litchar{lambda}

                          open @kleenestar[@nonterm{id}] close

                          @nonterm{expr} close]

                @nonterm{val})

          (list @nonterm{val}

                @BNF-alt[@nonterm{number} @nonterm{primop}])

          (list @nonterm{id}

                @elem{any name except for @litchar{lambda}})])

produces the output

 

‹expr›

 ::= 

‹id›

 

  |  

( ‹expr›+ )

 

  |  

( lambda ( ‹id›* ) ‹expr› )

 

  |  

‹val›

 

‹val›

 ::= 

‹number›  |  ‹primop›

 

‹id›

 ::= 

any name except for lambda

See also racketgrammar.

procedure

(BNF prod ...) → table?

  prod : (cons element? (listof (or/c block? element?)))
Typesets a grammar table. Each production starts with an element (typically constructed with nonterm) for the non-terminal being defined, and then a list of possibilities (typically constructed with BNF-seq, etc.) to show on separate lines.

procedure

(nonterm pre-content ...) → element?

  pre-content : any/c
Typesets a non-terminal: italic in angle brackets.

procedure

(BNF-seq elem ...) → element?

  elem : element?
Typesets a sequence.

procedure

(BNF-seq-lines elems ...) → block?

  elems : (listof element?)
Typesets a sequence that is broken into multiple lines, where each elems is one line.

procedure

(BNF-group pre-content ...) → element?

  pre-content : any/c
Typesets a group surrounded by curly braces (so the entire group can be repeated, for example).

procedure

(optional pre-content ...) → element?

  pre-content : any/c
Typesets an optional element: in square brackets.

procedure

(kleenestar pre-content ...) → element?

  pre-content : any/c
Typesets a 0-or-more repetition.

procedure

(kleeneplus pre-content ...) → element?

  pre-content : any/c
Typesets a 1-or-more repetition.

procedure

(kleenerange n m pre-content ...) → element?

  n : any/c
  m : any/c
  pre-content : any/c
Typesets a n-to-m repetition. The n and m arguments are converted to a string using (format "~a" n) and (format "~a" m).

procedure

(BNF-alt elem ...) → element?

  elem : element?
Typesets alternatives for a production’s right-hand side to appear on a single line. The result is normally used as a single possibility in a production list for BNF.

value

BNF-etc : string?

A string to use for omitted productions or content.

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