+ws ::= w** => ()
+ | w** "//" (~[\n]*) "\n" ws => ()
+wp ::= w++
+Grammar ::= r +/ ws => "grammar"
+
+r ::= word ^"::=" alternatives /ws
+ | word ^"!::=" alternatives /ws
+
+alternatives ::= (Conjuncts +/ (!ws "|" !ws)) +/ (!ws ">" !ws)
+
+Conjuncts ::= Sequence
+ | Sequence ^"&" e*/ws /ws
+ | Sequence ^"&~" e*/ws /ws
+
+ps ::= e*/ws => "ps"
+ | (e+/ws !ws)? "^" Quoted (!ws e+/ws)? => "ps2"
+psy ::= ps
+ | ps !wp ^"/" !ws e
+psx ::= psy => "psy"
+// | e "<-" psy /ws => "psyl"
+ | psy "->" e /ws => "psyr"
+// | e "<-" psy "->" e /ws => "psylr"
+Sequence ::= Quoted => "qprod"
+ > psx => "psx"
+ | psx "=>" ^"[]" /ws
+ | psx ^"=>" ("()"|word|Quoted) /ws
+
+ec ::= ~[\-\]\\]
+ | escaped
+
+Range ::= ec => "range"
+ | ec ^"-" ec
+
+e ::= word => "nonTerminal"
+ | Quoted => "literal"
+ | ^"()"
+ | ^"{" Sequence "}" /ws
+ | ^"[" Range* "]"
+
+ | (e ^"++" /ws > e ^"+" /ws)
+ | (e ^"++/" e /ws > e ^"+/" e /ws)
+ | (e ^"**" /ws > e ^"*" /ws)
+ | (e ^"**/" e /ws > e ^"*/" e /ws)
+ | ^"!" e /ws
+ | e ^"?" /ws
+
+ | "(" word ^")" /ws
+ > ^"(" alternatives ")" /ws
+ | ^"~" e
+
+word ::= [a-zA-Z0-9_]++
+Quoted ::= "\"" ((~[\"\\] | escaped)+) "\""
+ | "\"\"" => ""