Add memptyIfTrue/False functions

[vrom911]

memptyIfFalse should return mempty when the given predicate is unsatisfied (False), otherwise, return the default given value:

memptyIfFalse :: Monoid m => Bool -> m -> m

[srid]

Would this be a good addition?

memptyIfFalseM :: (Monad m, Monoid a) => m Bool -> m a -> m a

EDIT: What I meant to ask for was:

-- Current
whenJustM :: Monad m => m (Maybe a) -> (a -> m ()) -> m ()
-- New one
memptyIfNothingM :: (Monad m, Monoid a) => m (Maybe a) -> (a -> m a) -> m a

[chshersh]

@srid That sounds like an interesting proposal 🙂 I don't mind adding new combinators to relude, since at least the names don't conflict with anything. However, when adding new functions, we need to consider multiple things, so I encourage you to open a separate issue to discuss new functions, possible names and types, and especially use-cases.