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  • j

    jasoet-gdp

    01/22/2016, 9:20 AM
    i can just return it with 
    Nothing
  • j

    jasoet-gdp

    01/22/2016, 9:21 AM
    fun somMethod():UserDetail=Nothing
  • m

    mplatvoet

    01/22/2016, 9:21 AM
    sounds like a pretty bad thing todo?
  • m

    mplatvoet

    01/22/2016, 9:22 AM
    If something should return some type, it only should return that type
  • j

    jasoet-gdp

    01/22/2016, 9:26 AM
    yes, actually i realise that too.
  • d

    dmitry.petrov

    01/22/2016, 9:30 AM
    In Kotlin, 
    Nothing
    is also a subtype of every other type. And to mark a method "still pending", Kotlin has 
    TODO()
    .
  • e

    Eugenio

    01/22/2016, 9:34 AM
    Nothing
    is for when a function will never return, like when it throws an exception every time, otherwise it will be 
    Unit
    (like 
    void
    in Java)
  • m

    mplatvoet

    01/22/2016, 9:44 AM
    or if it forever blocks
  • n

    natpryce

    01/22/2016, 10:23 AM
    In Scala, if you can return Nothing as an expression, how does that relate to the type Nothing having no values? What does the expression 
    Nothing
    do?
  • n

    netme

    01/22/2016, 11:09 AM
    @netme has left the channel
  • e

    evanchooly

    01/22/2016, 1:42 PM
    Nothing
    sounds like a fancified 
    null
  • d

    dmitry.petrov

    01/22/2016, 1:43 PM
    Nope. In fact, it means "this expression never evaluates to a result". E.g., it always throws an exception.
  • e

    evanchooly

    01/22/2016, 1:43 PM
    no, i get that part. it just seems an odd construct.
  • e

    evanchooly

    01/22/2016, 1:44 PM
    a weird band-aid for odd subclassing corner cases perhaps?
  • d

    dmitry.petrov

    01/22/2016, 1:45 PM
    Not only simple smile. Among practical uses, that is 
    [[noreturn]]
    .
  • n

    natpryce

    01/22/2016, 2:24 PM
    @evanchooly: an example: System.exit returns Nothing. That cannot be expressed in Java, so I define in a Kotlin helper function with the correct type & calls the Java method.
  • e

    evanchooly

    01/22/2016, 2:25 PM
    it returns void, though.
  • e

    evanchooly

    01/22/2016, 2:25 PM
    well, declares it returns void. it obviously doesn’t actually return at all. simple smile
  • n

    natpryce

    01/22/2016, 2:30 PM
    It doesn't return void. It's declared to return void because the Java type system cannot express that it doesn't return. But Kotlin's can -- with the Nothing type
  • e

    evanchooly

    01/22/2016, 2:33 PM
    right. it’s just something i’ve never actually cared about it so I’m having hard time building the mental model of “why bother?"
  • e

    evanchooly

    01/22/2016, 2:33 PM
    i suppose it’s a nice way to say “make sure you don’t care about the thread this is running on"
  • n

    natpryce

    01/22/2016, 2:42 PM
    It lets the compiler detect dead code. Eg if a function returns Nothing, the following statements are dead code. IntelliJ will highlight it as a problem.
  • e

    evanchooly

    01/22/2016, 2:42 PM
    ah, now that’s a great point.
  • e

    evanchooly

    01/22/2016, 2:43 PM
    i hadn’t considered that aspect. thanks.
  • m

    mikehearn

    01/22/2016, 2:48 PM
    it also affects flow typing
  • m

    mikehearn

    01/22/2016, 2:48 PM
    if (a !is B) TODO()
  • m

    mikehearn

    01/22/2016, 2:48 PM
    a is now smart cast to B
  • e

    evanchooly

    01/22/2016, 2:54 PM
    ah. like scala’s 
    !!!
  • e

    evanchooly

    01/22/2016, 2:55 PM
    the more i use this language the sadder my day job makes me. 😄
  • m

    mikehearn

    01/22/2016, 3:01 PM
    what does !!! do?
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