Hacker News new | comments | show | ask | jobs | submit login

Don't Haskell and Scala also erase the types? If I remember correctly Martin Odersky even said erasure is better for some things in one of his videos/keynotes (?), but I'm not sure if I remember that correctly.



Haskell totally erased types and has a mechanism to recover that information as values. Both are way safer and easier to use than Java's versions.


Scala follows a similar route. It erases types, but lets you reify on demand in form of TypeTags.


Except not:

    x match {
      case _: List[Int] => 1
      case _: List[Char] => 2
      case _: String => 3
    }
This used java's semi-erased class tags and doesn't report a TypeTag constraint in its type. It will also return 1 when x is of type List[Char] since partial erasure means that the first two patterns end up being identical. The compiler will warn you about this situation, but generally it shows up all the time for various reasons. Super bad news.

That all said, the TypeTag system could be very nice someday. Especially if asInstanceOf were dropped eventually or, better, relied upon TypeTag.


Scala does. It's annoying in pattern matching clauses.


and yet it prevents you from shooting yourself in the foot at run time (if you have `-Xfatal-warnings` enabled), so the compiler has your back.

When Dotty and Java 10 land many annoyances will go away thankfully.




Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | DMCA | Apply to YC | Contact

Search: