Created
July 2, 2014 01:55
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Try at a Reader Monad in Swift
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| //this is a playground | |
| struct Reader<R,A> { | |
| let f:R -> A | |
| init(_ fun:R -> A) { | |
| f = fun | |
| } | |
| static func wrap(val:A) -> Reader<R,A> { | |
| return Reader({_ in val}) | |
| } | |
| func runReader(r:R) -> A { | |
| return f(r) | |
| } | |
| } | |
| func >>=<R,A,B>(w:Reader<R,A>, f:(R -> A) -> Reader<R,B>) -> Reader<R,B> { | |
| return f({(env:R) in w.runReader(env)}) | |
| } | |
| func hello() -> Reader<String, String> { | |
| return Reader({name in "Hello \(name)!"}) | |
| } | |
| func bye() -> Reader<String, String> { | |
| return Reader({name in "Bye \(name)!"}) | |
| } | |
| func both() -> Reader<String,String> { | |
| return Reader({name in hello().runReader(name) + " " + bye().runReader(name)}) | |
| } | |
| both().runReader("terry") |
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