; Compatible with https://www.quut.com/abnfgen/

; It's unclear whether this grammar is truly complete.  It has been
; verified not to produce text that is rejected by the Zisp parser
; --except for Unicode escape sequences for surrogate code points--
; but there may be some text that is accepted by the parser despite
; not being grammatical according to these rules.


Stream        = [ Unit *( Blank Unit ) ] *Blank [Trail]


Unit          = *Blank Datum

Blank         = HTAB / LF / %x0b / %x0c / CR / SP / Comment

Trail         = SkipLine / SkipUnit / ';' '~' *Blank


Datum         = BareString / DottedStr / CladDatum / Rune / RuneStr
              / RuneDotStr / RuneClad / LabelRef / LabelDef / HashStr
              / HashDotStr / HashClad / QuoteExpr / JoinExpr

Comment       = SkipLine LF / SkipUnit Blank

SkipLine      = ';' [ SkipLStart *AnyButLF ]

SkipUnit      = ';' '~' Unit

SkipLStart    = %x00-09 / %x0b-7d / %x7f-ff ; any but LF or '~'

AnyButLF      = %x00-09 / %x0b-ff


BareString    = BareChar *( BareChar / Numeric )

DottedStr     = ( '.' / Numeric ) *( '.' / Numeric / BareChar )

CladDatum     = '|' *( PipeStrChar / '\' StringEsc ) '|'
              / '"' *( QuotStrChar / '\' StringEsc ) '"'
              / '(' List ')'
              / '[' List ']'
              / '{' List '}'

Rune          = '#' RuneName

RuneStr       = '#' RuneName '\' BareString

RuneDotStr    = '#' RuneName '\' DottedStr

RuneClad      = '#' RuneName CladDatum

LabelRef      = '#' '%' Label '%'

LabelDef      = '#' '%' Label '=' Datum

HashStr       = '#' '\' BareString

HashDotStr    = '#' '\' DottedStr

HashClad      = '#' CladDatum

QuoteExpr     = "'" Datum
              / '`' Datum
              / ',' Datum

JoinExpr      = Datum RJoinDatum
              / LJoinDatum NoStartDot
              / Datum ':' Datum
              / NoEndDot '.' Datum


BareChar      = '!' / '$' / '%' / '*' / '/' / '<' / '=' / '>'
              / '?' / '@' / '^' / '_' / '~' / ALPHA

Numeric       = '+' / '-' / DIGIT

PipeStrChar   = %x00-5b / %x5d-7b / %x7d-ff ; any but '|' or '\'

QuotStrChar   = %x00-21 / %x23-5b / %x5d-ff ; any but '"' or '\'

StringEsc     = '\' / '|' / '"' / *( HTAB / SP ) LF *( HTAB / SP )
              / 'a' / 'b' / 't' / 'n' / 'v' / 'f' / 'r' / 'e'
              / 'x' 1*( 2HEXDIG ) ';'
              / 'u' ['0'] 1*5HEXDIG ';'
              / 'u' '1' '0' 4HEXDIG ';'

List          = [ Unit *( Blank Unit ) ] *Blank [Tail] [SkipUnit]

Tail          = '&' Unit *Blank


RuneName      = ALPHA *5( ALPHA / DIGIT )

Label         = 1*12( HEXDIG )


RJoinDatum    = CladDatum / Rune / RuneStr / RuneDotStr / RuneClad
              / LabelRef / LabelDef / HashStr / HashDotStr / HashClad
              / QuoteExpr

LJoinDatum    = CladDatum / RuneClad / LabelRef / HashClad

NoStartDot    = BareString / CladDatum / Rune / RuneStr / RuneDotStr
              / RuneClad / LabelRef / LabelDef / HashStr / HashDotStr
              / HashClad / QuoteExpr

NoEndDot      = BareString / Rune / RuneStr / RuneClad / LabelRef
              / HashStr / HashClad