> Even if you're sure it's not a Nothing, it might be better to use
>
> maybe (error "Impossible, because (...)") id

Which is the same thing as:

fromMaybe (error "Impossible, because (...)")

On Wed, Apr 22, 2015 at 1:23 PM, Marcin Mrotek <marcin.jan.mrotek@gmail.com> wrote:
Hello,

Well, you CAN use fromJust, but bear in mind that you should only use
it if you are absolutely, positively, 100% sure the Maybe value you
are calling fromJust on is of the form (Just something), because your
program will error out if you call fromJust on a Nothing. Even if
you're sure it's not a Nothing, it might be better to use

maybe (error "Impossible, because (...)") id

instead, so that you at the very least get a meaningful error message
in case "impossible" happens ;) Other than that, it's recomennded to
either use the maybe function, or pattern matching:

case foo of
  Just x -> ...
  Nothing -> ...

instead.

Best regards,
Marcin Mrotek
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