イテレーター非同期

イテレーター非同期

BeginCheckWithIteratorメソッドの実装ですが、これは単純に、Actionを先頭から実行していってる。

CPSをモナドと見るならば、sequence_ と同じ。
sequence_ はfoldrで実装されているので、同じようにするならこう。
（ただし、無駄にややこしい）

EnumerableEx.cs

    public static class EnumerableEx
    {
        public static TResult FoldRight<TSource, TResult>(this IEnumerable<TSource> source, TResult seed, Func<TSource, TResult, TResult> func)
        {
            Stack<TSource> stack = new Stack<TSource>(source);
            foreach (TSource element in stack)
                seed = func(element, seed);
            return seed;
        }

        public static TResult FoldRightStrict<TSource, TResult>(this IEnumerable<TSource> source, TResult seed, Func<TSource, TResult, TResult> func)
        {
            var iter = source.GetEnumerator();
            Func<TResult> rec = null;
            rec = () => (iter.MoveNext())
                ? func(iter.Current, rec())
                : seed;
            return rec();
        }

        public static TResult FoldRightNonStrict<TSource, TResult>(this IEnumerable<TSource> source, TResult seed, Func<Func<TSource>, Func<TResult>, TResult> nonStrictFunc)
        {
            var iter = source.GetEnumerator();
            Func<TResult> rec = null;
            rec = () => (iter.MoveNext())
                ? nonStrictFunc(() => iter.Current, rec)
                : seed;
            return rec();
        }
    }

CPS.cs

    public delegate void CPSAction(Action continuation);

    public static class CPS
    {
        public static CPSAction Bind(this CPSAction m, Func<CPSAction> k)
        {
            return c => m(() => k()(c));
        }

        public static CPSAction Sequence_(this IEnumerable<CPSAction> source)
        {
            CPSAction seed = c => c();
            Func<CPSAction, CPSAction, CPSAction> bindDiscard = (m, k) => m.Bind(() => k);
            return source.FoldRight(seed, bindDiscard);
        }

        public static CPSAction NonStrictSequence_(this IEnumerable<CPSAction> source)
        {
            CPSAction seed = c => c();
            Func<Func<CPSAction>, Func<CPSAction>, CPSAction> bindDiscard = (m, k) => m().Bind(() => k());
            return source.FoldRightNonStrict(seed, bindDiscard);
        }
    }

で、こう呼び出す。

CheckIterator(onComplete).NonStrictSequence_()(() => { });