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# Standard PEG notation
Stream <- Unit ( Blank Unit )* !.
Unit <- Blank* Datum
Blank <- [\t-\r ] / Comment
Datum <- OneDatum ( JoinChar? OneDatum )*
JoinChar <- '.' / ':'
Comment <- ';' ( SkipUnit / SkipLine )
SkipUnit <- '~' Unit
SkipLine <- (!'\n' .)* '\n'?
OneDatum <- BareString / CladDatum
BareString <- SpecBareChar ( BareChar / JoinChar )*
/ BareChar+
SpecBareChar <- '+' / '-' / JoinChar / DIGIT
BareChar <- ALPHA / DIGIT
/ '!' / '$' / '%' / '&' / '*' / '+' / '-' / '/'
/ '<' / '=' / '>' / '?' / '^' / '_' / '~'
CladDatum <- PipeStr / QuoteStr / HashExpr / QuoteExpr / List
PipeStr <- '|' ( PipeStrChar / '\' StringEsc )* '|'
QuoteStr <- '"' ( QuotStrChar / '\' StringEsc )* '"'
HashExpr <- '#' HashExprs
QuoteExpr <- "'" Datum / '`' Datum / ',' Datum
List <- ParenList / SquareList / BraceList
PipeStrChar <- (![|\\] .)
QuotStrChar <- (!["\\] .)
StringEsc <- '\' / '|' / '"' / ( HTAB / SP )* LF ( HTAB / SP )*
/ '0' / 'a' / 'b' / 't' / 'n' / 'v' / 'f' / 'r' / 'e'
/ 'x' HexByte* ';'
/ 'u' UnicodeSV ';'
HexByte <- HEXDIG HEXDIG
UnicodeSV <- HEXDIG+
HashExprs <- '!' [\t ]* HBangLine '\n'?
/ '%' Label ( '%' / '=' Datum )
/ '\' BareString / CladDatum
/ Rune ( '\' BareString / CladDatum )?
HBangLine <- HBChars+ [\t ]* ( HBChars+ )?
HBChars <- (![\t\n ] .)
Label <- HEXDIG+
Rune <- ALPHA ( ALPHA / DIGIT )*
ParenList <- '(' Unit* ')'
SquareList <- '[' Unit* ']'
BraceList <- '{' Unit* '}'
DIGIT <- [0-9]
ALPHA <- [a-zA-Z]
HEXDIG <- [0-9a-fA-F]
# Keep this in sync line-for-line with the ZBNF grammar for easy
# comparison between the two.
# This file is meant to be compatible with:
# https://piumarta.com/software/peg
# Due to a quirk in the peg tool this file is used with, the grammar
# must not allow an empty stream. Therefore, the Unit rule has its
# Datum declared as mandatory rather than optional.
# Local Variables:
# eval: (flyspell-mode -1)
# End:
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