| Line No. | Rev | Author | Line |
|---|---|---|---|
| 1 | 1 | paulosilva | |
| 2 | 7 | paulosilva | {-# LANGUAGE GADTs, PatternSignatures, FlexibleContexts #-} |
| 3 | 1 | paulosilva | {-# OPTIONS_GHC -Wall #-} |
| 4 | |||
| 5 | ------------------------------------------------------------------------------- | ||
| 6 | |||
| 7 | {- | | ||
| 8 | Module : Language.Type.Constraint | ||
| 9 | Description : Type equation constraints for type representation. | ||
| 10 | Copyright : (c) Paulo Silva | ||
| 11 | License : LGPL | ||
| 12 | |||
| 13 | Maintainer : paufil@di.uminho.pt | ||
| 14 | Stability : experimental | ||
| 15 | Portability : portable | ||
| 16 | |||
| 17 | -} | ||
| 18 | |||
| 19 | ------------------------------------------------------------------------------- | ||
| 20 | |||
| 21 | module Language.Type.Constraint ( | ||
| 22 | Constraint(..), | ||
| 23 | 3 | paulosilva | constraint2Rule, |
| 24 | 7 | paulosilva | typeRewrite, |
| 25 | typeRewriteE | ||
| 26 | 1 | paulosilva | ) where |
| 27 | |||
| 28 | 7 | paulosilva | import Control.GalcError |
| 29 | import Control.Monad.Error | ||
| 30 | 3 | paulosilva | import Control.MonadOr |
| 31 | 1 | paulosilva | import Language.Type.Equality |
| 32 | import Language.Type.Rewrite | ||
| 33 | import Language.Type.Syntax | ||
| 34 | |||
| 35 | ------------------------------------------------------------------------------- | ||
| 36 | |||
| 37 | data Constraint where | ||
| 38 | (:=:) :: Type a -> Type b -> Constraint | ||
| 39 | |||
| 40 | instance Show Constraint where | ||
| 41 | show (t1 :=: t2) = show t1 ++ " = " ++ show t2 | ||
| 42 | |||
| 43 | instance Eq Constraint where | ||
| 44 | (a :=: b) == (a' :=: b') = beq a a' && beq b b' | ||
| 45 | |||
| 46 | ------------------------------------------------------------------------------- | ||
| 47 | |||
| 48 | constraint2Rule :: Constraint -> Rule | ||
| 49 | constraint2Rule (t1 :=: t2) t1' = | ||
| 50 | if beq t1 t1' then return $ View t2 else mzero | ||
| 51 | |||
| 52 | ------------------------------------------------------------------------------- | ||
| 53 | |||
| 54 | 3 | paulosilva | typeRewrite :: MonadOr m => [Constraint] -> Type t -> m TypeBox |
| 55 | 1 | paulosilva | typeRewrite constr t = do |
| 56 | let rules::[Rule] = map constraint2Rule constr | ||
| 57 | 3 | paulosilva | return . view2Box =<< everywhere (try (seqRules rules)) t |
| 58 | 1 | paulosilva | |
| 59 | ------------------------------------------------------------------------------- | ||
| 60 | 7 | paulosilva | |
| 61 | typeRewriteE :: MonadError GalcError m => [Constraint] -> Type t -> m TypeBox | ||
| 62 | typeRewriteE constr t = | ||
| 63 | maybe2error (RewriteError (show t)) . typeRewrite constr $ t | ||
| 64 | |||
| 65 | ------------------------------------------------------------------------------- |