[Haskell-cafe] lens and Maybe value

[Tom Ellis]

On Tue, Dec 20, 2022 at 05:25:35PM +0100, PICCA Frederic-Emmanuel wrote:
> > Please clarify your question. Your code doesn't compile, and I can't tell
> > what it's supposed to do.
> 
> replace a (Maybe a) value in a data using lens only if the new (Maybe a) is a Just

How about

    over a (mb <|>)

?