public static Middleware <RR> SelectMany <T, R, RR>(this Middleware <T> mw, Func <T, Middleware <R> > bind, Func <T, R, RR> proj) => mw.Bind(t => bind(t).Map(r => proj(t, r)));
public static Middleware <RR> SelectMany <T, R, RR>(this Middleware <T> mw, Func <T, Middleware <R> > bind, Func <T, R, RR> proj) => mw.Bind(t => bind(t).Map(r => proj(t, r)));