Invercargill/src/lib/Queries/Transform.vala

namespace Invercargill {

    private class TransformQuery<Tin, Tout> : BaseQuery<Tin, Tout> {
        private TransformDelegate<Tin, Tout> transform_func;

        public TransformQuery(Enumerable<Tin> input, owned TransformDelegate<Tin, Tout> transform) {
            this.input = input;
            transform_func = (owned)transform;
        }

        //  public override bool iterate_if (Invercargill.PredicateDelegate<Tout> handler) {
        //      return input.iterate_if(i => handler(transform_func(i)));
        //  }

        public override Tracker<Tout> to_tracker() {
            var tracker = input.to_tracker();
            return new LambdaTracker<Tout>(
                () => tracker.has_next(),
                () => transform_func(tracker.get_next())
            );
        }
    }

}