| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Optics.Operators.Unsafe
Description
Synopsis
- (^?!) :: (HasCallStack, Is k An_AffineFold) => s -> Optic' k is s a -> a
Documentation
(^?!) :: (HasCallStack, Is k An_AffineFold) => s -> Optic' k is s a -> a infixl 8 Source #
Perform an *UNSAFE* head of an affine fold assuming that it is there.
>>>Left 4 ^?! _Left4
>>>"world" ^?! ix 3'l'
>>>[] ^?! _head*** Exception: (^?!): empty affine fold ...
Since: 0.3