/*
    Using generators here so your mileage may vary
 */

var makeIterable = function (iterator) {
  var iterable = {};
  iterable[Symbol.iterator] = iterator;
  return iterable;
};

/*
Function.method('curry', function (  ) {
    var slice = Array.prototype.slice,
        args = slice.apply(arguments),
        that = this;
    return function (  ) {
        return that.apply(null, args.concat(slice.apply(arguments)));
    };
});
*/
var curry = function () {
  // TODO
};

var compose = function () {
  // TODO
};

// transformers
var map = function (mapping, iterable) {
  return makeIterable ( function* () {
    for(let x of iterable) {
      yield mapping(x);
    }
  });
};

var filter = function (predicate, iterable) {
  return makeIterable ( function* () {
    for(let x of iterable) {
      if( predicate(x) ){
        yield x;
      }
    }
  });
};

var scan = function (accumulate, initValue, iterable) {
  // TODO
};

// terminators
var collect = function (iterable) {
  var arr = [];
  for(let x of iterable) {
    arr.push(x);
  }
  return arr;
}

var fold = function (accumulate, initValue, iterable) {
  // TODO
};

var each = function (action, iterable) {
  // TODO
};

//
// tests
//

var EXPECT_EQ = function (expected, actual) {
  // hacky way to compare stuff
  var e = JSON.stringify(expected);
  var a = JSON.stringify(actual);
  if (e !== a) {
    console.log('expected ' + e + ', got ' + a);
  }
};

EXPECT_EQ( [2, 4, 6], collect(map( (x) => x*2, [1, 2, 3])) );