deriving Show
instance Read Program where
- readPrec = fmap Program $ lift $ sepBy1 (readS_to_P reads) $ do
+ readPrec = fmap Program $ lift $ do
+ asts <- sepBy1 (readS_to_P reads) $ do
skipSpaces
char ';'
skipSpaces
+ optional $ char ';'
+ skipSpaces
+ return asts
data AST = Function String [String] Expr
+ | Extern String [String]
| Eval Expr
deriving Show
-data Expr = Num Float
+data Expr = Num Double
| BinOp BinOpType Expr Expr
| Var String
| Call String [Expr]
deriving Show
instance Read AST where
- readPrec = parseFunction +++ (Eval <$> readPrec)
- where parseFunction = lift $ do
- skipSpaces
- string "def"
- skipSpaces
+ readPrec = parseFunction +++ parseExtern +++ (Eval <$> readPrec)
+ where parseFunction = do
+ lift $ string "def" >> skipSpaces
+ (name, params) <- parsePrototype
+ lift skipSpaces
+ Function name params <$> readPrec
+ parseExtern = do
+ lift $ string "extern" >> skipSpaces
+ uncurry Extern <$> parsePrototype
+ parsePrototype = lift $ do
name <- munch1 isAlpha
params <- between (char '(') (char ')') $
sepBy (munch1 isAlpha) skipSpaces
- skipSpaces
- body <- readS_to_P reads
- return (Function name params body)
+ return (name, params)
instance Read Expr where
- readPrec = choice [ parseNum
+ readPrec = choice [ parseParens
+ , parseNum
, parseVar
, parseCall
, parseIf
, parseBinOp "<" (Cmp LT)
, parseBinOp "==" (Cmp EQ)
]
- where parseNum = Num <$> readPrec
+ where parseParens = step $ lift $
+ between (char '(') (char ')') (readS_to_P reads)
+ parseNum = Num <$> readPrec
parseVar = Var <$> lift (munch1 isAlpha)
parseCall = do
func <- lift (munch1 isAlpha)
(skipSpaces >> char ',' >> skipSpaces)
return (Call func params)
parseBinOp s typ = step $ do
- a <- prec 11 readPrec
+ a <- prec 11 readPrec -- set recursion limit of 11
lift $ do
skipSpaces
string s
skipSpaces
- b <- readPrec
- return (BinOp typ a b)
+ BinOp typ a <$> readPrec
parseIf = do
lift $ do
string "if"