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Manual. In the compilation field, textual representations like BNF or its variants are usually preferred. BNF is text-based, and used by compiler writers and parser generators. Railroad diagrams are visual, and may be more readily understood by laypeople, sometimes incorporated into graphic design.
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Each diagram has an entry point and an end point. The diagram describes possible paths between these two points by going through other nonterminals and terminals. Historically, terminals have been represented by round boxes and nonterminals by rectangular boxes but there is no official standard.
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The representation of a grammar is a set of syntax diagrams. Each diagram defines a "nonterminal" stage in a process. There is a main diagram which defines the language in the following way: to belong to the language, a word must describe a path in the main diagram.
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One possible syntax diagram for the example grammars is below. While the syntax for the text-based grammars differs, the syntax diagram for all of them can be the same because it is a
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279:"0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
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Note: the first link is sometimes blocked by the server outside of its domain, but it is available on
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format provides yet another example of a popular modern usage of these diagrams.
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46:. Early books using syntax diagrams include the "Pascal User Manual" written by
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We use arithmetic expressions as an example, in various grammar formats.
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SRFB Syntax
Diagram representation by Function Basis + svg generation
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Command AND Edit (CANDE) Language: Information Manual
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783:From EBNF to a postscript file with the diagrams
226:"x" | "y" | "z"
50:(diagrams start at page 47) and the Burroughs
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30:. They represent a graphical alternative to
16:Visual description of context-free grammar
803:Augmented Syntax Diagram (ASD) grammars
793:SQLite syntax diagram generator for SQL
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671:This format also supports ranges, e.g.
773:JSON website including syntax diagrams
812:Syntax Diagram Application Demo Site
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42:, and other text-based grammars as
55:The canonical source defining the
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798:Online Railroad Diagram Generator
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731:The Programming Language Pascal.
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617:ABNF also supports ranges, e.g.
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704:Recursive transition network
66:Principle of syntax diagrams
26:) are a way to represent a
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788:EBNF Parser & Renderer
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40:Augmented Backus–Naur form
709:Extended Backus–Naur form
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744:Burroughs B6700/B7700
28:context-free grammar
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733:(July 1973)
643:expression:
399:digit
378:constant
354:variable
342:expression
318:factor
303:term
288:expression
826:Categories
716:References
511:expression
472:expression
208:expression
126:expression
94:expression
810:Augmented
661:constant:
658:variable:
330:variable
324:constant
837:Diagrams
698:See also
538:constant
517:variable
502:variable
496:constant
262:constant
231:constant
218:variable
198:variable
188:constant
677:charset
655:factor:
626:%x30-39
309:factor
79:Example
808:(ASD)
711:(EBNF)
674:digit:
665:digit:
490:factor
487:factor
467:ABNF:
393:digit
384:digit
283:EBNF:
176:factor
157:factor
147:factor
649:term:
620:DIGIT
551:DIGIT
547:digit
294:term
271:digit
253:digit
243:digit
86:BNF:
52:CANDE
481:term
478:term
274:>
268:<
265:>
259:<
256:>
250:<
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240:<
234:>
228:<
221:>
215:<
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205:<
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185:<
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173:<
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167:term
164:<
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154:<
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132:<
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123:<
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116:term
113:<
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106:term
103:<
97:>
91:<
57:JSON
36:EBNF
22:(or
640:Red
277:::=
237:::=
224:::=
182:::=
141:::=
100:::=
828::
763:.
687:.
544:1*
396:};
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38:,
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402:=
390:{
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357:=
351:;
345:,
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333:|
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321:=
315:;
312:,
306:=
300:;
297:,
291:=
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