-s ::= ws grammar ws => "gram"
-ws !::= w**
-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 ^"?=>" e /ws
- | psy ^"!=>" e /ws
- > psy
-sequence ::= quoted => "qprod"
- > psx
- | psx ^"=>" (word|quoted) /ws
-
-ec ::= [~\-\]\\\~]
- | escaped
-
-range ::= ec => "range"
- | ec ^"-" ec
-
-e ::= word => "nonTerminal"
- | quoted => "literal"
- | ^"()"
- | ^"{" sequence "}" /ws
- | ^"[" range* "]"
- | ^"[~" range* "]"
-
- | (e ^"++" /ws > e ^"+" /ws)
- | (e ^"++/" e /ws > e ^"+/" e /ws)
- | (e ^"**" /ws > e ^"*" /ws)
- | (e ^"**/" e /ws > e ^"*/" e /ws)
- | e ^"?" /ws
-
- | "(" word ^")" /ws
- > ^"(" alternatives ")" /ws
-w !::= " "
- | "//" ([~\n]*) "\n"
- | "\n"
- | "\r"
-word ::= [a-zA-Z0-9_]+ !=> [a-zA-Z0-9_]
-quoted ::= "\"" (([~\"\\] | escaped)+) "\""
- | "\"\"" => ""
-escaped ::= "\\n" => "\n"
- | "\\r" => "\r"
- | "\\" [~nr]
+// use 'a'-'z' or 'a-z' instead of [a-z]?
+// EOF token?
+// #include (with renaming?)
+s = ws! Grammar ws!
+Grammar = Declaration +/ ws
+
+Declaration = NonTerminal
+ | ^"#import" ws! FileName (ws! "as" ws! Word)?
+
+FileName = FileNameChar+ -> [\r\n ]
+FileNameChar = Space:: "\\ "
+ | ~[\r\n ]
+
+NonTerminal = Word "=" RHS /ws
+ | Word "*" ws! ^"=" ws! RHS
+ | Word "*/" Word ws! ^"=" ws! RHS
+
+RHS = (Sequence +/ (ws! "|" ws!)) +/ (ws! ">" ws!)
+
+Elements = e*/ws
+
+PreSequence = Elements
+ | (Quoted|Word) ^"::" PreSequence /ws
+ > PreSequence ^"/" e /ws
+ | PreSequence ^"->" e /ws
+
+Sequence = psx:: PreSequence
+ | Sequence ^"&" Elements /ws
+ | Sequence ^"&~" Elements /ws
+
+ec = ~[\-\]\\]
+ | escaped
+
+Range = ec
+ | ec "-" ec
+
+e = (Quoted|Word) ^":" e
+ > NonTerminalReference
+ | Literal
+ | ^"()"
+ | ^"{" PreSequence "}" /ws
+ | ^"[" Range* "]"
+ | e ^"++" /ws -> ~[/]
+ | e ^"+" /ws -> ~[+]
+ | e ^"++/" e /ws
+ | e ^"+/" e /ws
+ | e ^"**" /ws -> ~[/]
+ | e ^"*" /ws -> ~[*]
+ | e ^"**/" e /ws
+ | e ^"*/" e /ws
+ | e ^"!"
+ | e ^"?" /ws
+ | ^"^" Quoted
+ > ^"(" RHS ")" /ws
+ | ^"~" e
+
+NonTerminalReference = Word
+Literal = Quoted
+Word = [.a-zA-Z0-9_]++
+Quoted = "\"" ((~[\"\\] | escaped)+) "\""
+ | EmptyString
+ EmptyString = "\"\""
+
+escaped = "\n":: "\\n"
+ | "\r":: "\\r"
+ | "\\" ~[nr]
+
+w = " " | "\n" | "\r"
+ws = w**
+ | w** "//" (~[\n])*! "\n" ws!
+wp = w++