26 lines
850 B
Org Mode
26 lines
850 B
Org Mode
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:PROPERTIES:
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:ID: 7a19b34d-c4bb-462b-8fae-581bf06dfdc4
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:END:
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#+title: Functor
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In [[id:9e68d422-cced-4177-96d1-90f777b9a493][Software Development]], this refers to a parameterized data type that wraps a
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value in a context and provides a method for applying a function to the wrapped
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value, independent of the container type.
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In [[id:9ac78677-2602-4a06-af0a-4ed82e98a9b6][Haskell]], the function for applying a function to a value in a functor is
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=fmap=, also available as the infix operator =<$>=.
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#+caption: =fmap= in Haskell
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#+begin_src haskell :exports code
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fmap :: Functor f => (a -> b) -> f a -> f b
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#+end_src
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* Examples
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** Maybe
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#+caption: Implementation of Functor for Maybe in Haskell
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#+begin_src haskell :exports code
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instance Functor Maybe where
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fmap func (Just n) = Just (func n)
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fmap func Nothing = Nothing
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#+end_src
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