#11441: RFC: Inline intermediate languages (Core, STG, Cmm, even StrictCore) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Allow intermediate code inline. == Inline ''Core'' == Typeable/WithTypeable:
{{{#!hs withTypeable :: TTypeRep a -> (Typeable a => r) -> r }}}
Currently, `withTypeable` cannot be written in Haskell, but it is straightforward to write in Core. Can we fix this?
We cannot implement ''withTypeable'' in Haskell source. But we ''can'' implement it in GHC's statically-typed intermediate language, System FC. The definition is simple, roughly like this:
{{{#!hs withTypeable tr k = k tr -- Not quite right }}}
Its second argument ''k'' expects a ''Typeable'' dictionary as its value argument. But since a ''Typeable'' dictionary is represented by a ''TypeRep'', we can simply
[http://www.seas.upenn.edu/~sweirich/papers/wadlerfest2016.pdf A reflection on types] (''2016''): pass ''tr'' to ''k''.
When written in System FC there is a type-safe coercion to move from ''TypeRep a'' to ''Typeable a'', but that coercion is erased at runtime. Since the definition can be statically type checked, ''withTypeable'' does not form part of the trusted code base.
== Inline ''Cmm'' == Edkward Kmett writes his own `.cmm` [https://github.com/ekmett/concurrent/blob/master/cbits/hashmap.cmm hither], [https://github.com/ekmett/concurrent/blob/master/cbits/array.cmm yon]. == Inline ''Strict Core'' == Should [http://research.microsoft.com/en-us/um/people/simonpj/papers /strict-core/tacc-hs09.pdf Types are calling conventions] (''2009'') be implemented:
=== '''4.4 The ''`seq`'' function''' ===
A nice feature of Strict Core,,ANF,, is that it is possible to give a straightforward definition of the primitive ''seq'' function of Haskell: {{{#!hs seq : {a:* -> b:* -> {a} -> {b} -> b} = { \a:*. \b:*. \x:{a}. \y:{b}. let _:a = x <> in y <> } }}}
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11441 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler