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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2015-04-09 15:02:08 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2015-04-09 17:36:59 +0100 |
| commit | 2d68aa650b2c47e011aaa7e51227491c3f1e9866 (patch) | |
| tree | 5d442e91827c26c5c12aef81b26391353fced604 | |
| parent | f536d89603bb49dea192b47f54416dc88da980af (diff) | |
| download | haskell-2d68aa650b2c47e011aaa7e51227491c3f1e9866.tar.gz | |
Comments about AnyK
| -rw-r--r-- | compiler/prelude/TysPrim.hs | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/compiler/prelude/TysPrim.hs b/compiler/prelude/TysPrim.hs index b1007e0224..19c64ef9cd 100644 --- a/compiler/prelude/TysPrim.hs +++ b/compiler/prelude/TysPrim.hs @@ -728,16 +728,20 @@ The type constructor Any of kind forall k. k has these properties: Note [Any kinds] ~~~~~~~~~~~~~~~~ - The type constructor AnyK (of sort BOX) is used internally only to zonk kind variables with no constraints on them. It appears in similar circumstances to Any, but at the kind level. For example: type family Length (l :: [k]) :: Nat - type instance Length [] = Zero -Length is kind-polymorphic, and when applied to the empty (promoted) list it -will have the kind Length AnyK []. + f :: Proxy (Length []) -> Int + f = .... + +Length is kind-polymorphic. So what is the elaborated type of f? + f :: Proxy (Length AnyK ([] AnyK)) -> Int + +Just like (length []) at the term level, which elaborates to + length (Any *) ([] (Any *)) Note [Strangely-kinded void TyCons] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |