sweet.js simple enum macro

enum_example.js

macro $enum {
  case $name:ident {$val:ident (,) ...} => {
    var $name = {$($val: null) (,) ...};
    for (var k in $name) {
      $name[k] = k;
    }
    Object.freeze($name);
  }
}

// Once sweet.js has syntax-case the for-loop
// will be unnecessary.

$enum Suites { CLUBS, SPADES, HEARTS, DIAMONDS }

// Equivalent to:
//
// var Suites = Object.freeze(
//   { CLUBS: 'CLUBS'
//   , SPADES: 'SPADES'
//   , HEARTS: 'HEARTS'
//   , DIAMONDS: 'DIAMONDS'
//   });

A "better" ident to string implementation could be the following:

macro to_string {
  case $x => { (JSON.stringify({ $x: 0 }).slice(2, -4)) }
}

macro enum {
  case [ $val:ident (,) ... ] => {
      (function () {
        var e = {
            $( $val : (to_string $val) ) (,) ...
        };
        Object.freeze(e);
        return e;
    })()
  }
}

console.dir(enum [ Hallo, World ]);