340 lines
10 KiB
Haskell
340 lines
10 KiB
Haskell
-- Interpreter for the Lamb programming language
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-- Copyright (c) 2013 darkf
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-- Licensed under the terms of the zlib license, see LICENSE for details
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module Interp where
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import Prelude hiding (lookup)
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import qualified Data.Map as M
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import qualified Data.ByteString.Char8 as BSC
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import qualified Network.Socket as SO
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import Data.List (intercalate)
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import Control.Monad.Trans (lift)
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import Control.Monad.Trans.State (StateT, runStateT, evalStateT, get, put)
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import System.IO (Handle, hPutStr, hGetLine, hFlush, hClose, hIsEOF, openBinaryFile, IOMode(..), stdout, stdin)
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import System.IO.Unsafe (unsafePerformIO)
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import AST
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import Parser (parseProgram)
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-- for Show
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newtype BIF = BIF (Value -> InterpState Value)
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instance Show BIF where show _ = "<built-in>"
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instance Eq BIF where a == b = False
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data Value = IntV Integer
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| StrV String
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| UnitV
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| BoolV Bool
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| StreamV Int
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| TupleV [Value]
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| ListV [Value]
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| Builtin BIF
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| FnV Env [(Pattern, AST)] -- closure pattern->body bindings
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deriving (Eq)
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type Env = [M.Map String Value] -- lexical environment (linked list)
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type InterpState = StateT ([Handle], Env) IO -- interpreter state (open handles, global env)
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emptyEnv = [M.empty]
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-- look up a binding from the bottom up
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lookup :: Env -> String -> Maybe Value
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lookup [] _ = Nothing
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lookup (env:xs) name =
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case M.lookup name env of
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Nothing -> lookup xs name
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Just x -> Just x
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-- bind in the local environment
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bind :: Env -> String -> Value -> Env
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bind (env:xs) name value = (M.insert name value env):xs
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instance Show Value where
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show (IntV i) = show i
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show (StrV s) = show s
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show (BoolV b) = show b
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show (TupleV v) = "(" ++ intercalate "," (map show v) ++ ")"
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show (ListV v) = show v
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show (FnV _ _) = "<fn>"
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show (StreamV _) = "<stream>"
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show (Builtin _) = "<built-in>"
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show UnitV = "()"
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-- value operators
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(IntV l) +$ (IntV r) = IntV (l + r)
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(StrV l) +$ (StrV r) = StrV (l ++ r)
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(ListV l) +$ (ListV r) = ListV (l ++ r)
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l +$ r = error $ "cannot + " ++ show l ++ " and " ++ show r
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(IntV l) -$ (IntV r) = IntV (l - r)
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l -$ r = error $ "cannot - " ++ show l ++ " and " ++ show r
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(IntV l) *$ (IntV r) = IntV (l * r)
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l *$ r = error $ "cannot * " ++ show l ++ " and " ++ show r
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(IntV l) /$ (IntV r) = IntV (l `div` r)
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l /$ r = error $ "cannot / " ++ show l ++ " and " ++ show r
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(IntV l) <$ (IntV r) = BoolV (l < r)
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l <$ r = error $ "cannot < " ++ show l ++ " and " ++ show r
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(IntV l) >$ (IntV r) = BoolV (l > r)
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l >$ r = error $ "cannot > " ++ show l ++ " and " ++ show r
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l ==$ r = BoolV (l == r)
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l !=$ r = BoolV (l /= r)
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-- some built-in functions
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_fputstr (TupleV [StreamV h, StrV str]) = do
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(handles,_) <- get
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let handle = handles !! h
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io <- lift $ hPutStr handle str >> hFlush handle
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return UnitV
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_fgetline (StreamV h) = do
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(handles,_) <- get
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let handle = handles !! h
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str <- lift $ hGetLine handle
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if last str == '\r' then -- remove trailing CR
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return . StrV $ init str
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else return $ StrV str
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_fread (TupleV [StreamV h, IntV n]) = do
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(handles,_) <- get
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let handle = handles !! h
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str <- lift $ BSC.hGet handle (fromIntegral n :: Int)
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return . StrV $ BSC.unpack str
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_fopen (TupleV [StrV path, StrV mode]) = do
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(handles,env) <- get
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let mode' = case mode of
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"r" -> ReadMode
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"w" -> WriteMode
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"rw" -> ReadWriteMode
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handle <- lift $ openBinaryFile path mode'
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put (handles ++ [handle], env)
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return . StreamV $ length handles
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_feof (StreamV h) = do
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(handles,_) <- get
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let handle = handles !! h
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isEof <- lift $ hIsEOF handle
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return $ BoolV isEof
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_fclose handle@(StreamV h) = do
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(handles,_) <- get
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let handle = handles !! h
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lift $ hClose handle
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return UnitV
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_sockopen (TupleV [StrV host, IntV port]) = do
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(handles,env) <- get
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handle <- lift $ SO.withSocketsDo $ do
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addr:_ <- SO.getAddrInfo Nothing (Just host) (Just $ show port)
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sock <- SO.socket (SO.addrFamily addr) SO.Stream SO.defaultProtocol
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SO.connect sock (SO.addrAddress addr)
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handle <- SO.socketToHandle sock ReadWriteMode
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return handle
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put (handles ++ [handle], env)
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return . StreamV $ length handles
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_putstr str@(StrV _) = _fputstr $ TupleV [StreamV 0, str]
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_getline UnitV = _fgetline (StreamV 1)
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_print v = _putstr $ StrV $ show v ++ "\n"
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_repr v = return . StrV $ show v
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_itos (IntV i) = return $ StrV $ show i
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_itos v = error $ "itos: not an int: " ++ show v
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_loop args@(TupleV [fn@(FnV _ _), arg]) = do
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v <- apply fn arg
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if v == BoolV True then
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_loop args
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else return UnitV
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_loop fn@(FnV _ _) = _loop $ TupleV [fn, UnitV]
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initialState = ([stdout, stdin],
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[M.fromList [("id", FnV emptyEnv [(VarP "x", Var "x")]),
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("loop", Builtin $ BIF _loop),
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("repr", Builtin $ BIF _repr),
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("stdout", StreamV 0),
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("stdin", StreamV 1),
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("print", Builtin $ BIF _print),
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("putstr", Builtin $ BIF _putstr),
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("putstrln", Builtin $ BIF (\x -> _putstr $ x +$ StrV "\n")),
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("getline", Builtin $ BIF _getline),
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("fgetline", Builtin $ BIF _fgetline),
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("fputstr", Builtin $ BIF _fputstr),
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("fread", Builtin $ BIF _fread),
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("feof", Builtin $ BIF _feof),
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("fclose", Builtin $ BIF _fclose),
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("fopen", Builtin $ BIF _fopen),
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("sockopen", Builtin $ BIF _sockopen),
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("itos", Builtin $ BIF _itos)]])
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eval :: AST -> InterpState Value
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eval (IntConst i) = return $ IntV i
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eval (StrConst s) = return $ StrV s
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eval (BoolConst b) = return $ BoolV b
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eval UnitConst = return UnitV
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eval (Block body) = foldr1 (>>) $ map eval body
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eval (Cons a b) = do
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a' <- eval a
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b' <- eval b
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case b' of
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ListV v' -> return $ ListV $ a':v'
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_ -> error "cons: RHS must be a list"
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eval (ListConst v) =
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mapM eval v >>= \xs ->
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return $ ListV xs
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eval (TupleConst v) = mapM eval v >>= return . TupleV
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eval (IfExpr c t e) = eval c >>= \cond ->
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case cond of
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BoolV True -> eval t
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BoolV False -> eval e
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_ -> error "if: condition must be a boolean"
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eval (Var var) = get >>= \(_,env) ->
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case lookup env var of
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Just v -> return v
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Nothing -> error $ "unbound variable " ++ var
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eval (Defun name fn) = do
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(s,env) <- get
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case lookup env name of
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Nothing -> -- bind new fn
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eval fn >>= \fn' ->
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put (s, bind env name fn') >> return fn'
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Just oldfn -> -- add pattern to old fn
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let FnV cls oldpats = oldfn
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Lambda [(pat, body)] = fn
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newfn = FnV cls (oldpats ++ [(pat, body)]) in
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put (s, bind env name newfn) >> return newfn
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eval (Def name v') = do
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v <- eval v'
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(s,env) <- get
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put (s, bind env name v)
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return v
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eval (Lambda pats) =
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get >>= \(_,env) ->
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if length env == 1 then -- if in global env just use [], denoting the current global scope
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return $ FnV [] pats
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else return $ FnV env pats
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eval (Add l r) = do { l <- eval l; r <- eval r; return $ l +$ r }
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eval (Sub l r) = do { l <- eval l; r <- eval r; return $ l -$ r }
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eval (Mul l r) = do { l <- eval l; r <- eval r; return $ l *$ r }
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eval (Div l r) = do { l <- eval l; r <- eval r; return $ l /$ r }
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eval (Equals l r) = do { l <- eval l; r <- eval r; return $ l ==$ r }
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eval (NotEquals l r) = do { l <- eval l; r <- eval r; return $ l !=$ r }
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eval (LessThan l r) = do { l <- eval l; r <- eval r; return $ l <$ r }
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eval (GreaterThan l r) = do { l <- eval l; r <- eval r; return $ l >$ r }
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eval (Call name arg) = get >>= \(h,env) ->
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case lookup env name of
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Just fn@(FnV cls _) -> do
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arg' <- eval arg
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let cls' = if cls == [] then [last env] else cls -- if [], use current global env
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put (h,cls') -- enter closure env
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v <- apply fn arg'
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put (h,env) -- restore env
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return v
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Just fn@(Builtin _) -> eval arg >>= apply fn
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Nothing -> error $ "call: name " ++ name ++ " doesn't exist or is not a function"
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eval x = error $ "eval: unhandled: " ++ show x
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patternBindings :: Pattern -> Value -> Maybe (M.Map String Value)
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patternBindings (VarP n) v = Just $ M.fromList [(n, v)]
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patternBindings (IntP n) (IntV v)
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| v == n = Just M.empty
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| otherwise = Nothing
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patternBindings (IntP n) _ = Nothing
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patternBindings UnitP UnitV = Just M.empty
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patternBindings UnitP _ = Nothing
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patternBindings (StrP x) (StrV y)
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| x == y = Just M.empty
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| otherwise = Nothing
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patternBindings (StrP _) _ = Nothing
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-- cons on strings
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patternBindings (ConsP x (ListP [])) (StrV (y:[])) = patternBindings x (StrV [y])
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patternBindings (ConsP xp xsp) (StrV (x:xs)) =
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do
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xe <- patternBindings xp (StrV [x])
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xse <- patternBindings xsp $ StrV xs
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Just $ M.union xe xse
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-- cons on lists
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patternBindings (ConsP x (ListP [])) (ListV (y:[])) = patternBindings x y
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patternBindings (ConsP xp xsp) (ListV (x:xs)) =
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do
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xe <- patternBindings xp x
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xse <- patternBindings xsp $ ListV xs
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Just $ M.union xe xse
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patternBindings (ConsP _ _) _ = Nothing
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-- lists
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patternBindings (ListP []) (ListV (x:_)) = Nothing -- not enough patterns
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patternBindings (ListP (_:_)) (ListV []) = Nothing -- not enough values
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patternBindings (ListP []) (ListV []) = Just M.empty -- base case
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patternBindings (ListP (x:xs)) (ListV (y:ys)) =
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do
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env <- patternBindings x y
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env' <- patternBindings (ListP xs) (ListV ys)
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Just $ M.union env' env
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patternBindings (ListP _) _ = Nothing -- not a list
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-- tuples
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patternBindings (TupleP []) (TupleV (x:_)) = Nothing -- not enough patterns
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patternBindings (TupleP (_:_)) (TupleV []) = Nothing -- not enough values
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patternBindings (TupleP []) (TupleV []) = Just M.empty -- base case
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patternBindings (TupleP (x:xs)) (TupleV (y:ys)) =
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do
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env <- patternBindings x y
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env' <- patternBindings (TupleP xs) (TupleV ys)
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Just $ M.union env' env
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patternBindings (TupleP _) _ = Nothing -- not a tuple
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-- applies a function
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apply :: Value -> Value -> InterpState Value
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apply (FnV _ pats) arg =
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apply' pats
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where
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apply' [] = error $ "argument " ++ show arg ++ " doesn't satisfy any patterns"
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apply' ((pat, body):xs) =
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case patternBindings pat arg of
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Just bindings -> -- satisfies
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do
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(s,env) <- get
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let newenv = bindings:env
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put (s, newenv)
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eval body
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Nothing -> -- doesn't satisfy this pattern
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apply' xs
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apply (Builtin (BIF fn)) arg = fn arg
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evalProgram :: [AST] -> IO Value -- fold the state from each node and return the result
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evalProgram nodes = evalStateT (foldr1 (>>) $ map eval nodes) initialState
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evalString :: String -> IO Value
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evalString program =
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case parseProgram program of
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Left err -> error $ show err
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Right prg -> evalProgram prg
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