Haskell conditional for | Hugonweb Annotated Link Bibliography

To only perform a monadic or applicative action if a value exists, you can use

for_ value $ action

So for example, if x is a Maybe String, you could print it if it exists with:

for_ x $ putStrLn x

I think that's the beauty of Haskell, this thing with a name from lists, when generalized to (Traversable) Applicatives, can do useful things for all kinds of things.

Since for_ is just traverse_ with it's arguments flipped, you could also do:

traverse_ (action) value

Keep in mind for_ and traverse_ are in Data.Foldable and not present in the Prelude.

Also, oddly, is the linked blog post scheduled to be published in the future?