#9214: UNPACK support for sum types -------------------------------------+------------------------------------- Reporter: mojojojo | Owner: osa1 Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1540 Wiki Page: UnpackedSumTypes | Phab:D1559 -------------------------------------+------------------------------------- Comment (by dfeuer): I'm just popping in to +1 this. Currently, `Data.IntMap` defines {{{#!hs data IntMap a = Bin ... !(IntMap a) !(IntMap a) | Tip ... | Nil }}} Logically, it *should* be {{{#!hs data IntMap a = IM !(IntMap1) | Nil data IntMap1 a = Bin ... !(IntMap1) !(IntMap1) | Tip ... }}} which would enforce the invariant that no `Nil`s can occur within a tree. But that has an extra indirection, which seems likely unacceptable. If we could `UNPACK` the `IntMap1` into the `IntMap`, we'd get the current performance with much nicer type guarantees. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9214#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler