define(['./_setup'], function (_setup) {

  // If Underscore is called as a function, it returns a wrapped object that can
  // be used OO-style. This wrapper holds altered versions of all functions added
  // through `_.mixin`. Wrapped objects may be chained.
  function _(obj) {
    if (obj instanceof _) return obj;
    if (!(this instanceof _)) return new _(obj);
    this._wrapped = obj;
  }

  _.VERSION = _setup.VERSION;

  // Extracts the result from a wrapped and chained object.
  _.prototype.value = function() {
    return this._wrapped;
  };

  // Provide unwrapping proxies for some methods used in engine operations
  // such as arithmetic and JSON stringification.
  _.prototype.valueOf = _.prototype.toJSON = _.prototype.value;

  _.prototype.toString = function() {
    return String(this._wrapped);
  };

  return _;

});