Unit          : Blank* ( Datum [Blank] | EOF )


Blank         : 9...13 | Comment

Datum         : OneDatum ( [JoinChar] OneDatum )*

JoinChar      : '.' | ':'


Comment       : ';' ( SkipUnit | SkipLine )

SkipUnit      : '~' Unit

SkipLine      : ( ~LF )* [LF]


OneDatum      : BareString | CladDatum

BareString    : ( '.' | '+' | '-' | DIGIT ) ( BareChar | '.' )*
              | BareChar+

CladDatum     : '|' PipeStrElt* '|'
              | '"' QuotStrElt* '"'
              | '#' HashExpr
              | '(' List ')' | '[' List ']' | '{' List '}'
              | "'" Datum | '`' Datum | ',' Datum


BareChar      : ALPHA | DIGIT
              | '!' | '$' | '%' | '&' | '*' | '+' | '-' | '/'
              | '<' | '=' | '>' | '?' | '@' | '^' | '_' | '~'


PipeStrElt    : ~( '|' | '\' ) | '\' StringEsc

QuotStrElt    : ~( '"' | '\' ) | '\' StringEsc

HashExpr      : Rune [ '\' BareString | CladDatum ]
              | '\' BareString
              | '%' Label ( '%' | '=' Datum )
              | CladDatum

List          : Unit* [ '.' Unit ] Blank*


StringEsc     : '\' | '|' | '"' | ( HTAB | SP )* LF ( HTAB | SP )*
              | 'a' | 'b' | 't' | 'n' | 'v' | 'f' | 'r' | 'e'
              | 'x' ( HEXDIG{2} )+ ';'
              | 'u' HEXDIG{1,6} ';'


Rune          : ALPHA ( ALPHA | DIGIT ){0,5}

Label         : HEXDIG{1,12}