Just package:ihaskell
Convert a possibly-incomplete specification for what to convert into
one which can be executed. Calls error when data is missing.
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.
The
isJust function returns
True iff its argument is of
the form
Just _.
Examples
Basic usage:
>>> isJust (Just 3)
True
>>> isJust (Just ())
True
>>> isJust Nothing
False
Only the outer constructor is taken into consideration:
>>> isJust (Just Nothing)
True