[GHC] #14196: Replace ArrayArray# with either UnliftedArray# or Array#
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Fri Sep 8 10:35:18 UTC 2017
#14196: Replace ArrayArray# with either UnliftedArray# or Array#
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Reporter: andrewthad | Owner: (none)
Type: feature request | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 8.2.1
Resolution: | Keywords:
| LevityPolymorphism
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Comment (by simonpj):
OK now I get it. I had to look at
[https://downloads.haskell.org/~ghc/7.4.2/docs/html/libraries/ghc-
prim-0.2.0.0/GHC-Prim.html#v:indexArrayArrayArray-35- the documentation
for ArrayArray#]. If I may say it like this:
The current primitive data type `ArrayArray#` is a heap-allocated array of
pointers to unlifted objects. Any kind of unlifted objects would be fine,
provide they are represented by a pointer. Specifically, we can put both
`Array#` and `ByteArray#` (and I suppose another `ArrayArray#`) inside an
`ArrayArray#`. But doing so is jolly awkwerd because `ArrayArray#` is not
a parameterised type.
Why isn't it parameterised? Becuase previously we had no way to quantify
over unlifted types. But now we do. So we can make `ArrayArray#` into a
paremterised type, namely your new
{{{
data UnliftedArray# (a :: TYPE 'UnliftedRep)
}}}
Your idea here is that `UniftedArray#` is an array of pointers to
''unlifted'' values.
Cool, I like it. Levity polymorphism is great.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14196#comment:3>
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