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| author | Joachim Breitner <mail@joachim-breitner.de> | 2013-09-13 18:40:36 +0200 |
|---|---|---|
| committer | Joachim Breitner <mail@joachim-breitner.de> | 2013-09-13 21:58:26 +0200 |
| commit | 17a868afa169c52d8525a95cbed87b2fc12044c6 (patch) | |
| tree | a04530408077a286a80ca8d34c5d6dc0c98eddc6 /compiler/coreSyn | |
| parent | 638da2fecaaaf743c4da7f8e2522f4afc0d8400c (diff) | |
| download | haskell-coercible.tar.gz | |
Introduce coerce :: Coercible a b -> a -> bcoercible
This is the result of the design at
http://ghc.haskell.org/trac/ghc/wiki/NewtypeWrappers
The goal is to be able to convert between, say [First Int] and [Last
Int] with zero run-time overhead. To that end, we introduce a special
two parameter type class Coercible whose instances are created
automatically and on-the fly. This relies on and exploits the recent
addition of roles to core.
Diffstat (limited to 'compiler/coreSyn')
| -rw-r--r-- | compiler/coreSyn/MkCore.lhs | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/compiler/coreSyn/MkCore.lhs b/compiler/coreSyn/MkCore.lhs index c6fc2be21f..656ffa8184 100644 --- a/compiler/coreSyn/MkCore.lhs +++ b/compiler/coreSyn/MkCore.lhs @@ -28,6 +28,9 @@ module MkCore ( -- * Constructing/deconstructing equality evidence boxes mkEqBox, + -- * Constructing Coercible evidence + mkCoercible, + -- * Constructing general big tuples -- $big_tuples mkChunkified, @@ -305,6 +308,11 @@ mkEqBox co = ASSERT2( typeKind ty2 `eqKind` k, ppr co $$ ppr ty1 $$ ppr ty2 $$ p where Pair ty1 ty2 = coercionKind co k = typeKind ty1 +mkCoercible :: Coercion -> CoreExpr +mkCoercible co = ASSERT2( typeKind ty2 `eqKind` k, ppr co $$ ppr ty1 $$ ppr ty2 $$ ppr (typeKind ty1) $$ ppr (typeKind ty2) ) + Var (dataConWorkId coercibleDataCon) `mkTyApps` [ty1, ty2] `App` Coercion co + where Pair ty1 ty2 = coercionKind co + k = typeKind ty1 \end{code} %************************************************************************ |