On Thu, Feb 16, 2012 at 4:25 PM, Johan Tibell
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.
By the way, I'd like to keep the two sources of reboxing separate. Users cannot do much about the reboxing that occurs due to using polymorphic data structures [1], such as Data.Map. However, the user can do something about reboxing due to lazy functions, namely making those functions stricter [2]. 1. In theory the user could create a cut-n-paste copy of the data structure and specialize it to a particular type, but I think we all agree that would be unfortunate (not to say that it cannot be justified in extreme cases.) 2. Although there might be cases when this isn't possible either, as in the case of non-specialized, non-inlined polymorphic functions. -- Johan