peg.txt

~grammar     = (ws r : rule)+ ws !. {{ result = ast_grammar(r, countr); }}

~ws          = (" " / "\n" / "\t")*

~wsp         = (" " / "\n" / "\t")+

~rule        = "~" <name> ws "=" ws b : body
    {{
      result = ast_rule(c(0), *b);
    }}

~name        = [A-Za-z0-9_]+

~body        = o : alt {{ result = *o; }}

~alt         = first : seq (ws "/" ws rest : seq)*
    {{
      result = ast_Alt(first, rest, countrest + 1);
    }}

~seq         = first : operator (wsp rest : operator)* 
    {{
      result = ast_Seq(first, rest, countrest + 1);
    }}

~operator    = o : prefix (ws "{{" ws <code> ws "}}")?
    {{
      if (ccount) { result = ast_with_code(c(0), *o); } else { result = *o; }
    }}
             / o : postfix (ws "{{" ws <code> ws "}}")?
    {{
      if (ccount) { result = ast_with_code(c(0), *o); } else { result = *o; }
    }}
             / o : group (ws "{{" ws <code> ws "}}")?
    {{
      if (ccount) { result = ast_with_code(c(0), *o); } else { result = *o; }
    }}

~prefix      = and ws o : group {{ result = ast_And(*o); }}
             / not ws o : group {{ result = ast_Not(*o); }}

~and         = "&"

~not         = "!"

~postfix     = o : group ws star {{ result = ast_Star(*o); }}
             / o : group ws plus {{ result = ast_Plus(*o); }}
             / o : group ws option {{ result = ast_Option(*o); }}

~star        = "*"

~plus        = "+"

~option      = "?"

~group       = "(" ws o : body ws ")" {{ result = *o; }}
             / "<" ws o : body ws ">" {{ result = ast_Capture(*o); }}
             / o : final {{ result = *o; }}

~final       = o : nonterminal {{ result = *o; }}
             / o : literal {{ result = *o; }}
             / o : cclass {{ result = *o; }}
             / o : dot {{ result = *o; }}

~nonterminal = <name> ws ":" ws <name>
    {{
      result = ast_AliasedNontm(c(1), c(0));
    }}
             / <name>
    {{
      result = ast_Nontm(c(0));
    }}

~literal     = "\"" <(&"\\" . . / !"\"" .)*> "\""
    {{
      result = ast_Literal(c(0));
    }}

~cclass      = "[" <(&"\\" . . / !"]" .)*> "]"
    {{
      result = ast_CClass(c(0));
    }}

~dot         = "." {{ result = ast_dot(); }}

~code        = (&"\\" . . / !"}}" .)*