import Data.Char
import Text.Read
-import Text.ParserCombinators.ReadP hiding ((+++), choice)
+import Text.ParserCombinators.ReadP hiding ((+++), (<++), choice)
newtype Program = Program [AST]
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]
| If Expr Expr Expr
+ | For String Expr Expr (Maybe Expr) Expr
deriving Show
data BinOpType = Add | Sub | Mul | Cmp Ordering
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 [ parseParens
, parseVar
, parseCall
, parseIf
+ , parseFor
, parseBinOp "+" Add
, parseBinOp "-" Sub
, parseBinOp "*" Mul
(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"
skipSpaces
elseE <- step readPrec
return (If cond thenE elseE)
+ parseFor = do
+ lift $ do
+ string "for"
+ skipSpaces
+ identifier <- lift (munch1 isAlpha)
+ lift $ skipSpaces >> char '=' >> skipSpaces
+ start <- step readPrec
+ lift $ skipSpaces >> char ',' >> skipSpaces
+ cond <- step readPrec
+ step' <- (do
+ lift $ skipSpaces >> char ',' >> skipSpaces
+ Just <$> step readPrec) <++ pure Nothing
+ lift $ skipSpaces >> string "in" >> skipSpaces
+ body <- step readPrec
+ return (For identifier start cond step' body)