132 lines
4.4 KiB
Haskell
132 lines
4.4 KiB
Haskell
-- | Evaluate simple literal expressions.
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module EvalLiterals where
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import Control.Monad.Error
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import Control.Monad.Identity
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import Control.Monad.State
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import Data.Bits
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import Data.Char
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import Data.Generics
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import Data.Int
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import Data.Maybe
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import Data.Word
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import Numeric
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import qualified AST as A
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import CompState
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import Errors
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type EvalM = ErrorT String (StateT CompState Identity)
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instance Die EvalM where
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die = throwError
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-- | Occam values of various types.
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data OccValue =
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OccBool Bool
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| OccByte Word8
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| OccInt Int32
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| OccInt16 Int16
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| OccInt32 Int32
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| OccInt64 Int64
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-- FIXME This should include the type of the elements, so we can handle
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-- empty arrays.
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| OccArray [OccValue]
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| OccRecord A.Name [OccValue]
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deriving (Show, Eq, Typeable, Data)
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-- | Is an expression a constant literal?
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isConstant :: A.Expression -> Bool
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isConstant (A.Literal _ _ (A.ArrayLiteral _ aes))
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= and $ map isConstantArray aes
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isConstant (A.Literal _ _ (A.RecordLiteral _ es))
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= and $ map isConstant es
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isConstant (A.Literal _ _ _) = True
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isConstant (A.True _) = True
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isConstant (A.False _) = True
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isConstant _ = False
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-- | Is an array literal element constant?
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isConstantArray :: A.ArrayElem -> Bool
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isConstantArray (A.ArrayElemArray aes) = and $ map isConstantArray aes
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isConstantArray (A.ArrayElemExpr e) = isConstant e
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-- | Evaluate a constant integer expression.
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evalIntExpression :: (CSM m, Die m) => A.Expression -> m Int
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evalIntExpression e
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= do ps <- get
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case runEvaluator ps (evalSimpleExpression e) of
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Left err -> die $ "cannot evaluate expression: " ++ err
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Right (OccInt val) -> return $ fromIntegral val
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Right _ -> die "expression is not of INT type"
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-- | Evaluate a byte literal.
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evalByte :: (CSM m, Die m) => String -> m Char
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evalByte s
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= do ps <- get
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case runEvaluator ps (evalByteLiteral s) of
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Left err -> die $ "cannot evaluate byte literal: " ++ err
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Right (OccByte ch) -> return (chr $ fromIntegral ch)
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-- | Run an evaluator operation.
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runEvaluator :: CompState -> EvalM OccValue -> Either String OccValue
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runEvaluator ps func
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= runIdentity (evalStateT (runErrorT func) ps)
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-- | Evaluate a simple literal expression.
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evalSimpleExpression :: A.Expression -> EvalM OccValue
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evalSimpleExpression e@(A.Literal _ _ _) = evalSimpleLiteral e
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evalSimpleExpression _ = throwError "not a literal"
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-- | Turn the result of one of the read* functions into an OccValue,
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-- or throw an error if it didn't parse.
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fromRead :: (t -> OccValue) -> (String -> [(t, String)]) -> String -> EvalM OccValue
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fromRead cons reader s
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= case reader s of
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[(v, "")] -> return $ cons v
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_ -> throwError $ "cannot parse literal: " ++ s
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-- | Evaluate a simple (non-array) literal.
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evalSimpleLiteral :: A.Expression -> EvalM OccValue
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evalSimpleLiteral (A.Literal _ A.Byte (A.ByteLiteral _ s))
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= evalByteLiteral s
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evalSimpleLiteral (A.Literal _ A.Byte (A.IntLiteral _ s))
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= fromRead OccByte (readSigned readDec) s
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evalSimpleLiteral (A.Literal _ A.Byte (A.HexLiteral _ s))
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= fromRead OccByte readHex s
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evalSimpleLiteral (A.Literal _ A.Int (A.IntLiteral _ s))
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= fromRead OccInt (readSigned readDec) s
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evalSimpleLiteral (A.Literal _ A.Int (A.HexLiteral _ s))
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= fromRead OccInt readHex s
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evalSimpleLiteral (A.Literal _ A.Int16 (A.IntLiteral _ s))
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= fromRead OccInt16 (readSigned readDec) s
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evalSimpleLiteral (A.Literal _ A.Int16 (A.HexLiteral _ s))
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= fromRead OccInt16 readHex s
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evalSimpleLiteral (A.Literal _ A.Int32 (A.IntLiteral _ s))
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= fromRead OccInt32 (readSigned readDec) s
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evalSimpleLiteral (A.Literal _ A.Int32 (A.HexLiteral _ s))
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= fromRead OccInt32 readHex s
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evalSimpleLiteral (A.Literal _ A.Int64 (A.IntLiteral _ s))
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= fromRead OccInt64 (readSigned readDec) s
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evalSimpleLiteral (A.Literal _ A.Int64 (A.HexLiteral _ s))
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= fromRead OccInt64 readHex s
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evalSimpleLiteral l = throwError $ "bad literal: " ++ show l
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-- | Evaluate a byte literal.
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evalByteLiteral :: String -> EvalM OccValue
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evalByteLiteral ('*':'#':hex)
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= do OccInt n <- fromRead OccInt readHex hex
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return $ OccByte (fromIntegral n)
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evalByteLiteral ['*', ch]
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= return $ OccByte (fromIntegral $ ord $ star ch)
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where
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star :: Char -> Char
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star 'c' = '\r'
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star 'n' = '\n'
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star 't' = '\t'
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star 's' = ' '
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star c = c
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evalByteLiteral [ch]
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= return $ OccByte (fromIntegral $ ord ch)
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evalByteLiteral _ = throwError "bad BYTE literal"
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