// Required by LINQ.
public static Cps <TResult, TContinuation> SelectMany <TSource, TSelector, TResult, TContinuation>
(this Cps <TSource, TContinuation> source,
Func <TSource, Cps <TSelector, TContinuation> > selector,
Func <TSource, TSelector, TResult> resultSelector) =>
continuation => source(sourceArg =>
selector(sourceArg)(selectorArg =>
continuation(resultSelector(sourceArg, selectorArg))));
// Not required, just for convenience.
public static Cps <TResult, TContinuation> SelectMany <TSource, TResult, TContinuation>
(this Cps <TSource, TContinuation> source, Func <TSource, Cps <TResult, TContinuation> > selector) =>
source.SelectMany(selector, Functions.False);
