:: Maybe a -> a package:ihaskell

fromJust :: HasCallStack => Maybe a -> a
ihaskell IHaskellPrelude
The fromJust function extracts the element out of a Just and throws an error if its argument is Nothing.

Examples

Basic usage: 
>>> fromJust (Just 1)
1

>>> 2 * (fromJust (Just 10))
20

>>> 2 * (fromJust Nothing)
*** Exception: Maybe.fromJust: Nothing
...
WARNING: This function is partial. You can use case-matching instead.