Hi, On 17.02.2012, at 09:52, Roman Leshchinskiy wrote:
Johan Tibell wrote:
The worry is that reboxing will cost us, but I realized today that at least one other language, Java, does this already today and even though it hurts performance in some cases, it seems to be a win on average. In Java all primitive fields get auto-boxed/unboxed when stored in polymorphic fields (e.g. in a HashMap which stores keys and fields as Object pointers.) This seems analogous to our case, except we might also unbox when calling lazy functions.
I'm not convinced that this is a good idea because it doesn't treat all types equally. The comparison with Java is problematic, IMO, because in Java 'int' is always called 'int' whereas in Haskell, it might be called many different things.
Actually, there are two types for every primitive type in Java: int / java.lang.Integer byte / java.lang.Byte char / java.lang.Char float / java.lang.Float double / java.lang.Double ... Starting with Java 5, javac automatically boxes / unboxes between a primitive type and its corresponding reference type. I.e. the programmer still specifies how a value is stored. This autoboxing simply makes them assignment compatible. As far as I understand it, auto boxing was introduced in order to better integrate primitive types with generics, not as an optimization. And I doubt that it is an optimization on average. I think, It might still be a good idea to realize Johann's proposal. I am just cautious whether Java really shows that this is a good idea. Regards, Jean