@function __create-aggregator-function-iteratee($value, $key, $collection) {
    $result: __this('result');
    $setter: __this('setter');
    $iteratee: __this('iteratee');
    $result: __exec($setter, $result, $value, __exec($iteratee, $value, $key, $collection), $collection);
    $_: __this('result', $result);

    @return true;
}


@function __create-aggregator-function($collection, $iteratee: '__identity', $this-arg: null) {
    $setter: __this('setter');
    $initializer: __this('initializer');
    $iteratee: __get-callback($iteratee, $this-arg, 3);
    $_: __this('iteratee', $iteratee);
    $result: if($initializer, __call($initializer), ());

    @if (__is-list($collection)) {
        $index: 1;
        $length: length($collection);

        @while ($index <= $length) {
            $value: nth($collection, $index);
            $result: __exec($setter, $result, $value, __exec($iteratee, $value, $index, $collection), $collection);
            $index: $index + 1;
        }
    } @else {
        $_: __this('result', $result);
        $_: __base-each($collection, '__create-aggregator-function-iteratee');
        $result: __this('result');
    }

    @return $result;
}


@function __create-aggregator($setter, $initializer: null) {
    $_: __scope((
        'setter': $setter,
        'initializer': $initializer
    ));
    $function: __bind('__create-aggregator-function');
    $_: __scope(false);

    @return $function;
}