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May 8, 2020 15:25
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These monad implemented in Elm
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| type These e a | |
| = Both ( e, a ) | |
| | Left e | |
| | Right a | |
| map : (a -> b) -> These e a -> These e b | |
| map f t = | |
| bimap ( identity, f ) t | |
| mapLeft : (e -> g) -> These e a -> These g a | |
| mapLeft f t = | |
| bimap ( f, identity ) t | |
| bimap : ( e -> g, a -> b ) -> These e a -> These g b | |
| bimap ( g, f ) t = | |
| case t of | |
| Left e -> | |
| Left (g e) | |
| Right a -> | |
| Right (f a) | |
| Both ( e, a ) -> | |
| Both ( g e, f a ) | |
| andThen : (a -> These e b) -> These e a -> These e b | |
| andThen f t = | |
| case t of | |
| Left e -> | |
| Left e | |
| Right a -> | |
| f a | |
| Both ( e, a ) -> | |
| case f a of | |
| Left _ -> | |
| Left e | |
| Right aa -> | |
| Right aa | |
| Both ( ee, aa ) -> | |
| Both ( ee, aa ) | |
| swap : These e a -> These a e | |
| swap t = | |
| case t of | |
| Left e -> | |
| Right e | |
| Right a -> | |
| Left a | |
| Both ( e, a ) -> | |
| Both ( a, e ) | |
| leftOnly : These e a -> Maybe e | |
| leftOnly t = | |
| unwrapLeft Nothing Just <| t | |
| rightOnly : These e a -> Maybe a | |
| rightOnly t = | |
| unwrap Nothing Just <| t | |
| unwrap : b -> (a -> b) -> These e a -> b | |
| unwrap default f t = | |
| case t of | |
| Left _ -> | |
| default | |
| Right a -> | |
| f a | |
| Both ( _, a ) -> | |
| f a | |
| unwrapLeft : g -> (e -> g) -> These e a -> g | |
| unwrapLeft default f t = | |
| case t of | |
| Left e -> | |
| f e | |
| Right _ -> | |
| default | |
| Both ( e, _ ) -> | |
| f e | |
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