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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #7647

UNPACK polymorphic fields

ticket:3990#comment:56197 mentions the possibility of unpacking polymorphic fields. To quote:

[…]

What I mean by "polymorphic unpack" is this:

  data Poly a = MkP Bool {-# UNPACK #-} a 
  data Mango = MkMango {-# UNPACK #-} (Poly Int)

Now a value of type Poly t would be represented using two pointer fields, as usual (ie the UNPACK would have no direct effect on Poly). But a Mango value would be represented thus:

  data Mango = MkMangoRep Bool Int#

  MkMango :: Poly Int -> MangoRep
  MkMango (MkP b (I# i)) = MkMangoRep b i

  -- Pattern match      (MkMango p -> rhs)
  -- is transformed to  (MkMangoRep b i -> let p = MkP b (I# i) in rhs

Something like that would be rather nice. This ticket is just a reminder.

Thanks,[[br]] /Liyang

Trac metadata
Trac field Value
Version 7.6.1
Type FeatureRequest
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related #3990 (closed)
Blocking
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