-s ::= ws grammar ws => "gram"
+s ::= grammar ws => "gram"
ws !::= w** | w** "//" (~[\n]*) "\n" ws
wp !::= w++
grammar ::= r +/ ws => "grammar"
| e "<-" psy "->" e /ws => "psylr"
sequence ::= quoted => "qprod"
> psx
+ | psx "=>" ^"[]" /ws
| psx ^"=>" (word|quoted) /ws
ec ::= ~[\-\]\\]