| I see, but then you can't have multiple fields, like | | ( (# Int,Bool #) |) | | You'd have to box the inner tuple too. Ok, I suppose. Well of course! It's just a parameterised data type, like a tuple. But, just like unboxed tuples, you could have an unboxed tuple (or sum) inside an unboxed tuple. (# (# Int,Bool #) | Int #) Simon | -----Original Message----- | From: Simon Marlow [mailto:marlowsd@gmail.com] | Sent: 08 September 2015 09:55 | To: Simon Peyton Jones; Johan Tibell; Ryan Newton | Cc: ghc-devs@haskell.org | Subject: Re: Unpacking sum types | | On 08/09/2015 09:31, Simon Peyton Jones wrote: | > | How did you envisage implementing anonymous boxed sums? What is | > | their heap representation? | > | > *Exactly* like tuples; that is, we have a family of data type | declarations: | > | > data (a|b) = (_|) a | > | (|_) b | > | > data (a|b|c) = (_||) a | > | (|_|) b | > | (||_) c | > ..etc. | | I see, but then you can't have multiple fields, like | | ( (# Int,Bool #) |) | | You'd have to box the inner tuple too. Ok, I suppose. | | Cheers | Simon | | | > Simon | > | > | | > | One option is to use some kind of generic object with a dynamic | > | number of pointers and non-pointers, and one field for the tag. | > | The layout would need to be stored in the object. This isn't a | > | particularly efficient representation, though. Perhaps there | could | > | be a family of smaller specialised versions for common sizes. | > | | > | Do we have a use case for the boxed version, or is it just for | > | consistency? | > | | > | Cheers | > | Simon | > | | > | | > | > Looks good to me! | > | > | > | > Simon | > | > | > | > *From:*Johan Tibell [mailto:johan.tibell@gmail.com] > *Sent:* | 01 | > | September 2015 18:24 > *To:* Simon Peyton Jones; Simon Marlow; | Ryan | > | Newton > *Cc:* ghc-devs@haskell.org > *Subject:* RFC: Unpacking | > | sum types > > I have a draft design for unpacking sum types that | > | I'd like some > feedback on. In particular feedback both on: | > | > | > | > * the writing and clarity of the proposal and | > | > | > | > * the proposal itself. | > | > | > | > https://ghc.haskell.org/trac/ghc/wiki/UnpackedSumTypes | > | > | > | > -- Johan | > | > | >