/// <summary>replicateM</summary>
public static Mayhap <IEnumerable <T> > Replicate <T>(this Mayhap <T> @this, int count)
{
// replicateM :: Applicative m => Int -> m a -> m [a]
// replicateM cnt0 f =
// loop cnt0
// where
// loop cnt
// | cnt <= 0 = pure []
// | otherwise = liftA2 (:) f (loop (cnt - 1))
//
// replicateM n act performs the action n times, gathering the results.
return(@this.Select(x => Enumerable.Repeat(x, count)));
}
/// <summary>mfilter</summary>
public static Mayhap <T> Where <T>(this Mayhap <T> @this, Func <T, bool> predicate)
{
// mfilter :: (MonadPlus m) => (a -> Bool) -> m a -> m a
// mfilter p ma = do
// a <- ma
// if p a then return a else mzero
//
// Direct MonadPlus equivalent of filter (for lists).
Utilities.Guard.NotNull(predicate, nameof(predicate));
// NB: x is never null.
return(@this.Bind(x => predicate(x) ? Mayhap <T> .Some(x) : Mayhap <T> .None));
}
