-s ::= ws grammar ws => "gram"
-ws !::= w**
-grammar ::= r $$ ws => "grammar"
-r ::= word ^"::=" alternatives /ws
- | word ^"!::=" alternatives /ws
-
-alternatives ::= equiAlt $$ (ws ">" ws)
-equiAlt ::= conjuncts $$ (ws "|" ws) => "alternatives"
-
-sequence ::= Es
- > Es ws ^"/" e
-Es ::= e %% (w**)
-es ::= e %% ws
-
-ss ::= es | es ^"/" e /ws
-
-conjuncts ::= rewrite
- | rewrite ^"&" e%%ws /ws
- | rewrite ^"&~" e%%ws /ws
-
-rewrite ::= sequence /ws => "rewrite"
- | sequence ^"=>" word /ws
- | sequence ^"=>" quoted /ws
- | sequence "=>" "()" /ws => "wrap"
-
-ec ::= [~\-\]\\\~]
- | escaped
-
-range ::= ec => "range0"
- | ec ^"-" ec => "range1"
-
-e ::= word => "nonTerminalY"
- | [(][)] => "epsilon"
- | ^"{" alternatives "}" /ws
- | "[" ranges "]" => "range"
- | "[~" ranges "]" => "rangex"
- | e ^"%%" e /ws
- | e ^"$$" e /ws
- | e ^"?" /ws
- | e ^"~/~" /ws
-
- | e ^"-" e /ws
-
- | ^"!" e /ws
- | "^" quoted /ws => "care"
- | ^"`" e /ws
- | e ^"#" /ws
- | quoted => "literal"
-
- | (e ws ^"**" > e ws ^"*")
- | (e ws ^"++" > e ws ^"+")
-
- | "(" word ^")" /ws
- > ^"(" alternatives ")" /ws
-
-ranges ::= range*
-
-w !::= " "
- | "//" [~\n]* "\n"
- | "\n"
- | "\r"
-an ::= [a-zA-Z0-9_]
-word ::= an++ => "sify"
-quoted ::= "\"" ([~\"\\] | escaped)* "\"" => "sify"
-escaped ::= "\\n" => "\n"
- | "\\r" => "\r"
- | "\\" [~nr]
-