ometa JSON {
  number    = <('-'                               )?
               ('0' | (digit:d ?(d != '0')) digit*)
               ('.' digit*                        )?
               (('E' | 'e') ('+' | '-')? digit*   )?>:f     -> parseFloat(f),
  hex       = char:x {this.intOfHexDigit(x)}:v   ?(v >= 0)  -> v,
  char      = :c ?(c != '"' && c != '\\')                   -> c
            | '\\' ( '"' | '\\'  | '/' -> '/' | 'n' -> '\n'
                   | 'b' -> '\b' | 'f' -> '\f'
                   | 'r' -> '\r' | 't' -> '\t'
                   | 'u' hex:a hex:b hex:c hex:d -> String.fromCharCode(4096*a + 256*b + 16*c + d)),
  string    = '"' char*:s '"'                               -> s.join(''),

  scanner   = spaces ( number:n                             -> [`num  , n    ]
                     | string:s                             -> [`str  , s    ]
                     | ``true''                             -> [`true , true ]
                     | ``false''                            -> [`false, false]
                     | ``null''                             -> [`null , null ]
                     | '{' | '}'| '[' | ']' | ',' | ':'),
  token  :t = scanner:s ?(t === s || t === s[0])            -> s,
  listOf :p = apply(p):e ("," apply(p))*:r                  -> [e].concat(r)
            |                                               -> [],

  value     = ("num" | "str" | "true" | "false" | "null"):v -> v[1]
            | array | object,
  key_value = ("str":s -> s[1]):k ":" value:v               -> [k, v],
  array     = "[" listOf('value'    ):l "]"                 -> l,
  object    = "{" listOf('key_value'):l "}"                 -> { var obj = {};
                                                                 for (var i = 0; i < l.length; i++)
                                                                   obj[l[i][0]] = l[i][1];
                                                                 obj }
}
JSON.intOfHexDigit = function(x) { return "0123456789abcdef".indexOf(x.toLowerCase()); };

JSON.matchAll('{"true\\n\\"\\u00a5": true, "foo": 42}', 'value')