mirror of
https://github.com/kanaka/mal.git
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c9c504ac20
Split user functions and macros, merge user functions and core functions. Add a flag triggering debugging info in EVAL. Reserve mutable environments for REPL and let*. Move env type declaration from Types to Env. Check let* arguments only once. Share more code between map constructions and key type checks. Stop copying metadata when evaluating collections. The strict variant of Data.Map.Strict is recommended for general use. simplify printer.
153 lines
4.6 KiB
Haskell
153 lines
4.6 KiB
Haskell
import System.IO (hFlush, stdout)
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import Control.Monad.Except (liftIO, runExceptT)
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import Data.Foldable (foldlM)
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import Readline (addHistory, readline, load_history)
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import Types
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import Reader (read_str)
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import Printer(_pr_list, _pr_str)
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import Env (Env, env_apply, env_get, env_let, env_put, env_repl, env_set)
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import Core (ns)
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--
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-- Set this to True for a trace of each call to Eval.
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--
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traceEval :: Bool
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traceEval = False
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-- read
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mal_read :: String -> IOThrows MalVal
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mal_read = read_str
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-- eval
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let_bind :: Env -> [MalVal] -> IOThrows ()
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let_bind _ [] = return ()
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let_bind env (MalSymbol b : e : xs) = do
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liftIO . env_set env b =<< eval env e
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let_bind env xs
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let_bind _ _ = throwStr "invalid let*"
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apply_ast :: MalVal -> [MalVal] -> Env -> IOThrows MalVal
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apply_ast (MalSymbol "def!") [MalSymbol a1, a2] env = do
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evd <- eval env a2
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liftIO $ env_set env a1 evd
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return evd
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apply_ast (MalSymbol "def!") _ _ = throwStr "invalid def!"
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apply_ast (MalSymbol "let*") [MalSeq _ _ params, a2] env = do
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let_env <- liftIO $ env_let env
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let_bind let_env params
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eval let_env a2
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apply_ast (MalSymbol "let*") _ _ = throwStr "invalid let*"
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apply_ast (MalSymbol "do") args env = foldlM (const $ eval env) Nil args
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apply_ast (MalSymbol "if") [a1, a2, a3] env = do
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cond <- eval env a1
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eval env $ case cond of
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Nil -> a3
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MalBoolean False -> a3
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_ -> a2
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apply_ast (MalSymbol "if") [a1, a2] env = do
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cond <- eval env a1
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case cond of
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Nil -> return Nil
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MalBoolean False -> return Nil
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_ -> eval env a2
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apply_ast (MalSymbol "if") _ _ = throwStr "invalid if"
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apply_ast (MalSymbol "fn*") [MalSeq _ _ params, ast] env = return $ MalFunction (MetaData Nil) fn where
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fn :: [MalVal] -> IOThrows MalVal
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fn args = do
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case env_apply env params args of
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Just fn_env -> eval fn_env ast
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Nothing -> do
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p <- liftIO $ _pr_list True " " params
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a <- liftIO $ _pr_list True " " args
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throwStr $ "actual parameters: " ++ a ++ " do not match signature: " ++ p
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apply_ast (MalSymbol "fn*") _ _ = throwStr "invalid fn*"
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apply_ast first rest env = do
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evd <- eval env first
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case evd of
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MalFunction _ f -> f =<< mapM (eval env) rest
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_ -> throwStr . (++) "invalid apply: " =<< liftIO (_pr_list True " " $ first : rest)
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eval :: Env -> MalVal -> IOThrows MalVal
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eval env ast = do
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case traceEval of
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True -> liftIO $ do
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putStr "EVAL: "
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putStr =<< _pr_str True ast
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putStr " "
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env_put env
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putStrLn ""
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hFlush stdout
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False -> pure ()
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case ast of
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MalSymbol sym -> do
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maybeVal <- liftIO $ env_get env sym
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case maybeVal of
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Nothing -> throwStr $ "'" ++ sym ++ "' not found"
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Just val -> return val
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MalSeq _ (Vect False) (a1 : as) -> apply_ast a1 as env
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MalSeq _ (Vect True) xs -> MalSeq (MetaData Nil) (Vect True) <$> mapM (eval env) xs
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MalHashMap _ xs -> MalHashMap (MetaData Nil) <$> mapM (eval env) xs
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_ -> return ast
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-- print
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mal_print :: MalVal -> IOThrows String
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mal_print = liftIO . Printer._pr_str True
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-- repl
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rep :: Env -> String -> IOThrows String
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rep env line = mal_print =<< eval env =<< mal_read line
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repl_loop :: Env -> IO ()
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repl_loop env = do
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line <- readline "user> "
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case line of
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Nothing -> return ()
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Just "" -> repl_loop env
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Just str -> do
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addHistory str
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res <- runExceptT $ rep env str
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out <- case res of
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Left mv -> (++) "Error: " <$> liftIO (Printer._pr_str True mv)
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Right val -> return val
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putStrLn out
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hFlush stdout
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repl_loop env
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-- Read and evaluate a line. Ignore successful results, but crash in
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-- case of error. This is intended for the startup procedure.
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re :: Env -> String -> IO ()
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re repl_env line = do
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res <- runExceptT $ eval repl_env =<< mal_read line
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case res of
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Left mv -> error . (++) "Startup failed: " <$> Printer._pr_str True mv
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Right _ -> return ()
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defBuiltIn :: Env -> (String, Fn) -> IO ()
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defBuiltIn env (sym, f) =
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env_set env sym $ MalFunction (MetaData Nil) f
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main :: IO ()
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main = do
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load_history
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repl_env <- env_repl
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-- core.hs: defined using Haskell
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mapM_ (defBuiltIn repl_env) Core.ns
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-- core.mal: defined using the language itself
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re repl_env "(def! not (fn* (a) (if a false true)))"
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repl_loop repl_env
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