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# This is a file defining the BPEG grammar using BPEG syntax
Grammar: __ *(Def [__`;])%__ __ ($$ / @!={... => "Could not parse this code"})
Def: @name=id _ `: __ (
@definition=extended-pat
/ $$ @!={=>"No definition for rule"}
/ @!={...>(`;/id_`:/$) => "Invalid definition: @0"})
# This is used for command line arguments:
String-pattern: ... % (Nodent / Escape / `\ pat [`;])
pat: simple-pat !(__("!="/"==")) / suffixed-pat
simple-pat: Upto-and / Dot / String / Chars / Nodent / Escape-range
/ Escape / Repeat / Optional / After / Before / Capture / Replace
/ Ref / parens
suffixed-pat: (
Eq-pat
/ Not-eq-pat
)
Eq-pat: @first=pat__"=="__@second=pat
Not-eq-pat: @first=pat__"!="__@second=pat
Dot: `. !`.
String: (
`" @s=*(Escape / !`".) (`" / @!={=> "Expected closing quote here"})
/ `' @s=*(Escape / !`'.) (`' / @!={=> "Expected closing quote here"})
)
Chars: `` @+(Char/Char-range) % `,
Char-range: @low=. `- (@high=. / @!={=> "Expected a second character to form a character range"})
Char: (@s=. / @!={=> "Expected a character following the '`'"})
Escape-range: `\ @low=escape-sequence `- @high=escape-sequence
Escape: `\ (@s=escape-sequence
/ $ @!={=>"Backslashes are used for escape sequences, not splitting lines"}
/ @!={. *(Abc/`0-9) => "Invalid escape sequence: '@0'"}
)
escape-sequence: (
`n,t,r,e,b,a,v
/ 1-3 `0-7
/ `x 2 `0-9,a-f,A-F
)
No: `! (_@pat / @!={=>"Expected a pattern after the exclamation mark"})
Nodent: `\ `N
Upto-and: 2-3`. [_@first=simple-pat] [__`%__@second=simple-pat]
Repeat: (
@min='' `* @max=''
/ @min=int _ `- _ @max=int
/ @min=int _ `+ @max=''
/ @min=@max=int
) __ @repeat-pat=pat [__`%__@sep=pat]
Optional: `[ __ extended-pat (__`] / @!={=> "Expected closing square bracket here"})
After: `< _ pat
Before: `> _ pat
Capture: `@ [_ @capture-name=(id/`!) __ !"=>" `=] __ (@capture=pat / @!={=> "Expected pattern to capture"})
Replace: `{ __ (
[@replace-pat=extended-pat __] "=>" [__ @replacement=String]
) __ (`} / @!={=> "Expected closing brace here"})
Ref: @name=id !(_`:)
parens: `( __ extended-pat (__ `) / @!={=> "Expected closing parenthesis here"})
Chain: 2+@pat%__
Otherwise: 2+@(Chain/pat)%(__`/__)
extended-pat: Otherwise / Chain / pat
# Special-symbol rules:
_: *(` / \t)
__: *(` / \t / \r / \n / comment)
$$: !$.
$: !.
^^: !<$.
^: !<.
id: "^^" / "^" / "__" / "_" / "$$" / "$" / "|" / `a-z,A-Z *`a-z,A-Z,0-9,-
line-comment: `# .. $
block-comment: "#("..")#" % block-comment
# Note: comments are undefined by default in regular BPEG
comment: block-comment / line-comment
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