Documentation

The fromJust function extracts the element out of a Just and throws an error if its argument is Nothing.

Examples

>>> fromJust (Just 1)
1

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

>>> 2 * (fromJust Nothing)
*** Exception: Maybe.fromJust: Nothing

The read function reads input from a string, which must be completely consumed by the input process. read fails with an error if the parse is unsuccessful, and it is therefore discouraged from being used in real applications. Use readMaybe or readEither for safe alternatives.

>>> read "123" :: Int
123

>>> read "hello" :: Int
*** Exception: Prelude.read: no parse

Convert from an Int.

the predecessor of a value. For numeric types, pred subtracts 1.

the successor of a value. For numeric types, succ adds 1.