optics-core-0.4.1.1: Optics as an abstract interface: core definitions
Safe HaskellSafe-Inferred
LanguageHaskell2010

Optics.Operators.Unsafe

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Synopsis

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 ^?! _Left
4
>>> "world" ^?! ix 3
'l'
>>> [] ^?! _head
*** Exception: (^?!): empty affine fold
...

Since: 0.3