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%
% (c) The AQUA Project, Glasgow University, 1996
%
\section[Kind]{The @Kind@ datatype}
\begin{code}
#include "HsVersions.h"
module Kind (
Kind(..), -- Only visible to friends: TcKind
mkArrowKind,
mkTypeKind,
mkUnboxedTypeKind,
mkBoxedTypeKind,
hasMoreBoxityInfo,
resultKind, argKind,
pprKind, pprParendKind,
isUnboxedTypeKind, isTypeKind, isBoxedTypeKind,
notArrowKind
) where
IMP_Ubiq(){-uitous-}
import Util ( panic, assertPanic )
--import Outputable ( Outputable(..) )
import Pretty
\end{code}
\begin{code}
data Kind
= TypeKind -- Any type (incl unboxed types)
| BoxedTypeKind -- Any boxed type
| UnboxedTypeKind -- Any unboxed type
| ArrowKind Kind Kind
deriving Eq
mkArrowKind = ArrowKind
mkTypeKind = TypeKind
mkUnboxedTypeKind = UnboxedTypeKind
mkBoxedTypeKind = BoxedTypeKind
isTypeKind :: Kind -> Bool
isTypeKind TypeKind = True
isTypeKind other = False
isBoxedTypeKind :: Kind -> Bool
isBoxedTypeKind BoxedTypeKind = True
isBoxedTypeKind other = False
isUnboxedTypeKind :: Kind -> Bool
isUnboxedTypeKind UnboxedTypeKind = True
isUnboxedTypeKind other = False
hasMoreBoxityInfo :: Kind -> Kind -> Bool
BoxedTypeKind `hasMoreBoxityInfo` TypeKind = True
BoxedTypeKind `hasMoreBoxityInfo` BoxedTypeKind = True
UnboxedTypeKind `hasMoreBoxityInfo` TypeKind = True
UnboxedTypeKind `hasMoreBoxityInfo` UnboxedTypeKind = True
TypeKind `hasMoreBoxityInfo` TypeKind = True
kind1@(ArrowKind _ _) `hasMoreBoxityInfo` kind2@(ArrowKind _ _) = ASSERT( kind1 == kind2 )
True
-- The two kinds can be arrow kinds; for example when unifying
-- (m1 Int) and (m2 Int) we end up unifying m1 and m2, which should
-- have the same kind.
kind1 `hasMoreBoxityInfo` kind2 = False
notArrowKind (ArrowKind _ _) = False
notArrowKind other_kind = True
resultKind :: Kind -> Kind -- Get result from arrow kind
resultKind (ArrowKind _ res_kind) = res_kind
resultKind other_kind = panic "resultKind"
argKind :: Kind -> Kind -- Get argument from arrow kind
argKind (ArrowKind arg_kind _) = arg_kind
argKind other_kind = panic "argKind"
\end{code}
Printing
~~~~~~~~
\begin{code}
instance Outputable Kind where
ppr sty kind = pprKind kind
pprKind TypeKind = ppStr "**" -- Can be boxed or unboxed
pprKind BoxedTypeKind = ppStr "*"
pprKind UnboxedTypeKind = ppStr "*#" -- Unboxed
pprKind (ArrowKind k1 k2) = ppSep [pprParendKind k1, ppStr "->", pprKind k2]
pprParendKind k@(ArrowKind _ _) = ppBesides [ppLparen, pprKind k, ppRparen]
pprParendKind k = pprKind k
\end{code}
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