DrawGrammar
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Published
20 hours ago •
jacquev6
jacquev6
Support for IETF RFC 5234
Just curious, where the computer science industry stand so far on this variant of BNF syntax called IETF RFC5234 for its ABNF syntax scheme?
And whether or not it becomes a worthy feature candidate here.
An example of ABNF is found in the Python community for TOML specification (a solidly used specification by a majority of the Python community) using Github's own ABNF code syntax highlighter below:
https://github.com/toml-lang/toml/blob/1.0.0/toml.abnf
;; This document describes TOML's syntax, using the ABNF format (defined in
;; RFC 5234 -- https://www.ietf.org/rfc/rfc5234.txt).
;;
;; All valid TOML documents will match this description, however certain
;; invalid documents would need to be rejected as per the semantics described
;; in the supporting text description.
;; It is possible to try this grammar interactively, using instaparse.
;; http://instaparse.mojombo.com/
;;
;; To do so, in the lower right, click on Options and change `:input-format` to
;; ':abnf'. Then paste this entire ABNF document into the grammar entry box
;; (above the options). Then you can type or paste a sample TOML document into
;; the beige box on the left. Tada!
;; Overall Structure
toml = expression *( newline expression )
expression = ws [ comment ]
expression =/ ws keyval ws [ comment ]
expression =/ ws table ws [ comment ]
;; Whitespace
ws = *wschar
wschar = %x20 ; Space
wschar =/ %x09 ; Horizontal tab
;; Newline
newline = %x0A ; LF
newline =/ %x0D.0A ; CRLF
;; Comment
comment-start-symbol = %x23 ; #
non-ascii = %x80-D7FF / %xE000-10FFFF
non-eol = %x09 / %x20-7F / non-ascii
comment = comment-start-symbol *non-eol
;; Key-Value pairs
keyval = key keyval-sep val
key = simple-key / dotted-key
simple-key = quoted-key / unquoted-key
unquoted-key = 1*( ALPHA / DIGIT / %x2D / %x5F ) ; A-Z / a-z / 0-9 / - / _
quoted-key = basic-string / literal-string
dotted-key = simple-key 1*( dot-sep simple-key )
dot-sep = ws %x2E ws ; . Period
keyval-sep = ws %x3D ws ; =
val = string / boolean / array / inline-table / date-time / float / integer
;; String
string = ml-basic-string / basic-string / ml-literal-string / literal-string
;; Basic String
basic-string = quotation-mark *basic-char quotation-mark
quotation-mark = %x22 ; "
basic-char = basic-unescaped / escaped
basic-unescaped = wschar / %x21 / %x23-5B / %x5D-7E / non-ascii
escaped = escape escape-seq-char
escape = %x5C ; \
escape-seq-char = %x22 ; " quotation mark U+0022
escape-seq-char =/ %x5C ; \ reverse solidus U+005C
escape-seq-char =/ %x62 ; b backspace U+0008
escape-seq-char =/ %x66 ; f form feed U+000C
escape-seq-char =/ %x6E ; n line feed U+000A
escape-seq-char =/ %x72 ; r carriage return U+000D
escape-seq-char =/ %x74 ; t tab U+0009
escape-seq-char =/ %x75 4HEXDIG ; uXXXX U+XXXX
escape-seq-char =/ %x55 8HEXDIG ; UXXXXXXXX U+XXXXXXXX
;; Multiline Basic String
ml-basic-string = ml-basic-string-delim [ newline ] ml-basic-body
ml-basic-string-delim
ml-basic-string-delim = 3quotation-mark
ml-basic-body = *mlb-content *( mlb-quotes 1*mlb-content ) [ mlb-quotes ]
mlb-content = mlb-char / newline / mlb-escaped-nl
mlb-char = mlb-unescaped / escaped
mlb-quotes = 1*2quotation-mark
mlb-unescaped = wschar / %x21 / %x23-5B / %x5D-7E / non-ascii
mlb-escaped-nl = escape ws newline *( wschar / newline )
;; Literal String
literal-string = apostrophe *literal-char apostrophe
apostrophe = %x27 ; ' apostrophe
literal-char = %x09 / %x20-26 / %x28-7E / non-ascii
;; Multiline Literal String
ml-literal-string = ml-literal-string-delim [ newline ] ml-literal-body
ml-literal-string-delim
ml-literal-string-delim = 3apostrophe
ml-literal-body = *mll-content *( mll-quotes 1*mll-content ) [ mll-quotes ]
mll-content = mll-char / newline
mll-char = %x09 / %x20-26 / %x28-7E / non-ascii
mll-quotes = 1*2apostrophe
;; Integer
integer = dec-int / hex-int / oct-int / bin-int
minus = %x2D ; -
plus = %x2B ; +
underscore = %x5F ; _
digit1-9 = %x31-39 ; 1-9
digit0-7 = %x30-37 ; 0-7
digit0-1 = %x30-31 ; 0-1
hex-prefix = %x30.78 ; 0x
oct-prefix = %x30.6F ; 0o
bin-prefix = %x30.62 ; 0b
dec-int = [ minus / plus ] unsigned-dec-int
unsigned-dec-int = DIGIT / digit1-9 1*( DIGIT / underscore DIGIT )
hex-int = hex-prefix HEXDIG *( HEXDIG / underscore HEXDIG )
oct-int = oct-prefix digit0-7 *( digit0-7 / underscore digit0-7 )
bin-int = bin-prefix digit0-1 *( digit0-1 / underscore digit0-1 )
;; Float
float = float-int-part ( exp / frac [ exp ] )
float =/ special-float
float-int-part = dec-int
frac = decimal-point zero-prefixable-int
decimal-point = %x2E ; .
zero-prefixable-int = DIGIT *( DIGIT / underscore DIGIT )
exp = "e" float-exp-part
float-exp-part = [ minus / plus ] zero-prefixable-int
special-float = [ minus / plus ] ( inf / nan )
inf = %x69.6e.66 ; inf
nan = %x6e.61.6e ; nan
;; Boolean
boolean = true / false
true = %x74.72.75.65 ; true
false = %x66.61.6C.73.65 ; false
;; Date and Time (as defined in RFC 3339)
date-time = offset-date-time / local-date-time / local-date / local-time
date-fullyear = 4DIGIT
date-month = 2DIGIT ; 01-12
date-mday = 2DIGIT ; 01-28, 01-29, 01-30, 01-31 based on month/year
time-delim = "T" / %x20 ; T, t, or space
time-hour = 2DIGIT ; 00-23
time-minute = 2DIGIT ; 00-59
time-second = 2DIGIT ; 00-58, 00-59, 00-60 based on leap second rules
time-secfrac = "." 1*DIGIT
time-numoffset = ( "+" / "-" ) time-hour ":" time-minute
time-offset = "Z" / time-numoffset
partial-time = time-hour ":" time-minute ":" time-second [ time-secfrac ]
full-date = date-fullyear "-" date-month "-" date-mday
full-time = partial-time time-offset
;; Offset Date-Time
offset-date-time = full-date time-delim full-time
;; Local Date-Time
local-date-time = full-date time-delim partial-time
;; Local Date
local-date = full-date
;; Local Time
local-time = partial-time
;; Array
array = array-open [ array-values ] ws-comment-newline array-close
array-open = %x5B ; [
array-close = %x5D ; ]
array-values = ws-comment-newline val ws-comment-newline array-sep array-values
array-values =/ ws-comment-newline val ws-comment-newline [ array-sep ]
array-sep = %x2C ; , Comma
ws-comment-newline = *( wschar / [ comment ] newline )
;; Table
table = std-table / array-table
;; Standard Table
std-table = std-table-open key std-table-close
std-table-open = %x5B ws ; [ Left square bracket
std-table-close = ws %x5D ; ] Right square bracket
;; Inline Table
inline-table = inline-table-open [ inline-table-keyvals ] inline-table-close
inline-table-open = %x7B ws ; {
inline-table-close = ws %x7D ; }
inline-table-sep = ws %x2C ws ; , Comma
inline-table-keyvals = keyval [ inline-table-sep inline-table-keyvals ]
;; Array Table
array-table = array-table-open key array-table-close
array-table-open = %x5B.5B ws ; [[ Double left square bracket
array-table-close = ws %x5D.5D ; ]] Double right square bracket
;; Built-in ABNF terms, reproduced here for clarity
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
DIGIT = %x30-39 ; 0-9
HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
One can use the following to do Github ABNF syntax highlighting:
```abnf
;; Built-in ABNF terms, reproduced here for clarity
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
DIGIT = %x30-39 ; 0-9
HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
```
Just curious, where the computer science industry stand so far on this variant of BNF syntax called IETF RFC5234 for its ABNF syntax scheme?
I have no idea.
And whether or not it becomes a worthy feature candidate here.
Worthy indeed. I've not worked on this project for a while though, so I'm not going to implement this myself. But I would spend a few hours to merge a PR and deploy it to http://jacquev6.github.io/DrawGrammar. And to OPAM if the process has not changed too much since last time.
