Browse Source

Added example JSON parser.

redux
David Majda 13 years ago
parent
commit
a1adbf0607
  1. 104
      examples/json.pegjs

104
examples/json.pegjs

@ -0,0 +1,104 @@
/* JSON parser based on the grammar described at http://json.org/. */
/* ===== Syntactical Elements ===== */
start: _ object { return $2; }
object
: "{" _ "}" _ { return {}; }
/ "{" _ members "}" _ { return $3; }
members: pair ("," _ pair)* {
var result = {};
result[$1[0]] = $1[1];
for (var i = 0; i < $2.length; i++) {
result[$2[i][2][0]] = $2[i][2][1];
}
return result;
}
pair: string ":" _ value { return [$1, $4]; }
array
: "[" _ "]" _ { return []; }
/ "[" _ elements "]" _ { return $3; }
elements: value ("," _ value)* {
var result = [$1];
for (var i = 0; i < $2.length; i++) {
result.push($2[i][2]);
}
return result;
}
value
: string
/ number
/ object
/ array
/ "true" _ { return true; }
/ "false" _ { return false; }
// FIXME: We can't return null here because that would mean parse failure.
/ "null" _ { return "null"; }
/* ===== Lexical Elements ===== */
string "string"
: '"' '"' _ { return ""; }
/ '"' chars '"' _ { return $2; }
chars: char+ { return $1.join(""); }
char
// In the original JSON grammar: "any-Unicode-character-except-"-or-\-or-control-character"
: [^"\\\0-\x1F\x7f]
/ '\\"' { return '"'; }
/ "\\\\" { return "\\"; }
/ "\\/" { return "/"; }
/ "\\b" { return "\b"; }
/ "\\f" { return "\f"; }
/ "\\n" { return "\n"; }
/ "\\r" { return "\r"; }
/ "\\t" { return "\t"; }
/ "\\u" hexDigit hexDigit hexDigit hexDigit {
return String.fromCharCode(parseInt("0x" + $2 + $3 + $4 + $5));
}
number "number"
: int frac exp _ { return parseFloat($1 + $2 + $3); }
/ int frac _ { return parseFloat($1 + $2); }
/ int exp _ { return parseFloat($1 + $2); }
/ int _ { return parseFloat($1); }
int
: digit19 digits { return $1 + $2; }
/ digit
/ "-" digit19 digits { return $1 + $2 + $3; }
/ "-" digit { return $1 + $2; }
frac: "." digits { return $1 + $2; }
exp: e digits { return $1 + $2; }
digits: digit+ { return $1.join(""); }
e: [eE] [+-]? { return $1 + $2; }
/*
* The following rules are not present in the original JSON gramar, but they are
* assumed to exist implicitly.
*/
digit: [0-9]
digit19: [1-9]
hexDigit: [0-9a-fA-F]
/* ===== Whitespace ===== */
_ "whitespace": whitespace*
// Whitespace is undefined in the original JSON grammar, so I assume a simple
// conventional definition.
whitespace: [ \t\n\r]
Loading…
Cancel
Save