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A comment on Scrap Your Cake Pattern Boilerplate: Dependency Injection Using the Reader Monad. Parent comment

Re:Scrap Your Cake Pattern Boilerplate: Dependency Injection... by jarhart on Monday October 28, 2013 @04:20PM (#6629496)
Technically, Scala's for comprehensions don't let you mix monads either, but implicit conversions make it work in some cases. For example, there's an implicit conversion from Option to Iterable so the Option (Maybe) and List monads can be mixed. It's really more a matter of Scala's type system allowing it. The Scala compiler just re-writes comprehensions into equivalent higher-order function application.
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Re:Scrap Your Cake Pattern Boilerplate: Dependency Injection... by kilovoltaire on Monday October 28, 2013 @04:33PM (#6629581)
Cool thanks, didn't realize it was due to implicits. Here are my tests, for the record.

Works in Scala:

    for {a <- Seq(Some(1), None, Some(3)); b <- a} yield b
Doesn't work in Haskell:

    do a <- [Just 1, Nothing, Just 3]; b <- a; return b
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