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{-# LANGUAGE LambdaCase #-}
module Evaluator (
evaluate,
) where
import qualified Data.Map as M
import qualified Data.List as L
import Data.Function ( on )
import Control.Monad.Reader
import Control.Monad.Except ( catchError )
import Utils
-- import Debug.Trace
_curryCall :: Env -> [AST] -> LFunction -> LContext AST
_curryCall _ [] f = return $ (makeNonsenseAST $ ASTFunction f)
_curryCall env (arg:[]) f = f env arg
_curryCall env (arg:rest) f = do
g <- _curryCall env rest f
case astNode g of
ASTFunction f' -> f' env arg
other -> throwL (astPos g) $ "cannot call value " ++ show other ++ " as a function"
curryCall :: Env -> [AST] -> LFunction -> LContext AST
curryCall env [] f = f env (makeNonsenseAST ASTUnit)
curryCall env args f = _curryCall env args f
traverseAndReplace :: String -> AST -> AST -> AST
traverseAndReplace param arg ast@AST { astNode = ASTSymbol sym }
| sym == param = arg
| otherwise = ast
traverseAndReplace param arg ast@AST { astNode = ASTFunctionCall body } =
ast { astNode = ASTFunctionCall $ (map (traverseAndReplace param arg) body) }
traverseAndReplace param arg ast@AST { astNode = ASTVector vec } =
ast { astNode = ASTVector $ (map (traverseAndReplace param arg) vec) }
traverseAndReplace param arg ast@AST { astNode = ASTHashMap hmap } =
ast { astNode = ASTHashMap $ M.assocs hmap
$> L.concatMap (\(a, b) -> [a, b])
.> map (traverseAndReplace param arg)
.> asPairs .> M.fromList }
traverseAndReplace _ _ other = other
foldSymValPairs :: [(String, AST)] -> AST -> AST
foldSymValPairs [] body = body
foldSymValPairs ((sym, val):rest) body =
let replacedRestVals = map (snd .> traverseAndReplace sym val) rest
replacedRest = zip (map fst rest) (replacedRestVals)
replacedBody = traverseAndReplace sym val body
in foldSymValPairs replacedRest replacedBody
letArgsToSymValPairs :: Env -> [AST] -> LContext (String, AST)
letArgsToSymValPairs env args =
case args of
[AST { astNode = ASTSymbol symbol' }, value'] -> do
(_, evaledValue) <- evaluate env value'
return (symbol', evaledValue)
[AST { astNode = ASTSymbol "lazy" }, AST { astNode = ASTSymbol symbol' }, value'] -> do
return (symbol', value')
other -> throwL (astPos $ head other) $ "let called with invalid args " ++ show other
defineUserFunction :: AST -> [AST] -> LContext LFunction
defineUserFunction AST { astNode = ASTSymbol param } exprs = return fn where
fn :: LFunction
fn env arg = do
let replacedExprs = map (traverseAndReplace param arg) exprs
let letExprs = take (length exprs - 1) replacedExprs
letSymValPairs <- letExprs
$> mapM (\case AST { astNode = ASTFunctionCall v } -> return $ drop 1 v
ast -> throwL (astPos ast) $ "unreachable: map letExprs, ast: " ++ show ast)
.> fmap (mapM $ letArgsToSymValPairs env) .> join
let body = head $ drop (length exprs - 1) replacedExprs
let newBody = traverseAndReplace param arg body
$> foldSymValPairs letSymValPairs
(_, ret) <- evaluate env newBody
return ret
defineUserFunction param exprs = throwL (astPos param)
$ "unreachable: defineUserFunction, param: " ++ show param ++ ", exprs: " ++ show exprs
defineUserFunctionWithLetExprs :: [AST] -> [AST] -> LContext LFunction
defineUserFunctionWithLetExprs [] exprs =
-- the position info is nonsensical, but it should never get read anyway
defineUserFunction (makeNonsenseAST $ ASTSymbol "unit") exprs
defineUserFunctionWithLetExprs (param:[]) exprs =
defineUserFunction param exprs
defineUserFunctionWithLetExprs (AST { astNode = ASTSymbol param }:rest) exprs = return fn where
fn :: LFunction
fn _ arg = do
let newExprs = map (traverseAndReplace param arg) exprs
ret <- defineUserFunctionWithLetExprs rest newExprs
-- the returned AST will not have the correct position info, but that's fine
-- because the info is overridden in evaluateFunctionDef anyway
return $ makeNonsenseAST $ ASTFunction $ ret
defineUserFunctionWithLetExprs (param:_) _ = throwL (astPos $ param)
$ "unreachable: defineUserFunctionWithLetExprs, param: " ++ show param
evaluateFunctionDef :: Env -> [AST] -> LContext (Env, AST)
evaluateFunctionDef env asts = do
let defAst = head asts
args = tail asts
(params'', exprs) <- case args of
args'
| length args' < 2 ->
throwL (astPos defAst) $ "\\ called with " ++ show (length args) ++ " arguments"
| otherwise -> return $ (head args', tail args')
AST { astNode = ASTVector params' } <- assertIsASTVector params''
params <- mapM assertIsASTSymbol params'
let shadowingParamM = L.find (astNode .> (\(ASTSymbol sym) -> sym) .> isParamNameShadowing) params
case shadowingParamM of
Just shadowingParam -> throwL (astPos shadowingParam)
$ "parameter is shadowing already defined symbol " ++ show (astNode shadowingParam)
Nothing -> return ()
let letExprs = take (length exprs - 1) exprs
let nonLetExprM = L.find (not . isLetAST) letExprs
case nonLetExprM of
Just nonLetExpr -> throwL (astPos nonLetExpr)
$ "non-let expression in function definition before body: " ++ show nonLetExpr
Nothing -> return ()
fn <- defineUserFunctionWithLetExprs params exprs
return $ (env, defAst { astNode = ASTFunction fn })
where
isLetAST AST { astNode = ASTFunctionCall (AST { astNode = ASTSymbol "let" }:_) } = True
isLetAST _ = False
isParamNameShadowing name = M.member name env
evaluateMatch :: Env -> [AST] -> LContext (Env, AST)
evaluateMatch env asts = do
let matchAst = head asts
args = tail asts
(actualExpr, rest) <- case args of
[] -> throwL (astPos matchAst) $ "match called with no arguments"
(_:[]) -> throwL (astPos matchAst) "empty match cases"
(a:b) -> return (a, b)
pairs <- (asPairsM rest) `catchError`
(\_ -> throwL (astPos matchAst) $ "invalid number of arguments passed to match\n"
++ "- matching on expr: " ++ show actualExpr ++ "\n"
++ "- arguments: " ++ show rest)
(_, evaledActual) <- evaluate env actualExpr
ret <- matchPairs (actualExpr, evaledActual) pairs
return (env, matchAst { astNode = astNode ret })
where
matchPairs :: (AST, AST) -> [(AST, AST)] -> LContext AST
matchPairs (actualExpr, evaledActual) [] = throwL (astPos actualExpr)
$ "matching case not found when matching on expression: " ++ show actualExpr
++ " (actual value: " ++ show evaledActual ++ ")"
matchPairs (actualExpr, evaledActual) ((matcher, branch):restPairs) = do
(_, evaledMatcher) <- evaluate env matcher
if evaledActual == evaledMatcher
then do
(_, ret) <- evaluate env branch
return ret
else matchPairs (actualExpr, evaledActual) restPairs
evaluateLet :: Env -> [AST] -> LContext (Env, AST)
evaluateLet env asts = do
let letAst = head asts
args = tail asts
(symbol, value) <- letArgsToSymValPairs env args
when (M.member symbol env) $ throwL (astPos letAst) $ "symbol already defined: " ++ symbol
let newEnv = M.insert symbol value env
return $ (newEnv, letAst { astNode = ASTUnit })
evaluateEnv :: Env -> [AST] -> LContext (Env, AST)
evaluateEnv env asts = do
let envAst = head asts
let pairs = M.assocs env
let longestKey = L.maximumBy (compare `on` (length . fst)) pairs $> fst
let pad s = s ++ take (length longestKey + 4 - length s) (L.repeat ' ')
let rows = pairs $> map (\(k, v) -> pad k ++ show v)
liftIO $ mapM_ putStrLn rows
return (env, envAst { astNode = ASTUnit })
evaluateUserFunction :: Env -> [AST] -> LContext (Env, AST)
evaluateUserFunction env children = do
let fnAst = head children
args = tail children
(_, fnEvaled) <- evaluate env fnAst
AST { astNode = (ASTFunction fn) } <- assertIsASTFunction fnEvaled
evaledArgs' <- mapM (evaluate env) args
let evaledArgs = map snd evaledArgs'
doubleEvaledArgs' <- mapM (evaluate env) evaledArgs
let doubleEvaledArgs = map snd doubleEvaledArgs'
result <- curryCall env (reverse doubleEvaledArgs) fn
-- maybe remove double eval here? can't remember why it was added
return (env, fnAst { astNode = astNode result })
evaluateSymbol :: Env -> AST -> LContext (Env, AST)
evaluateSymbol env ast@AST { astNode = ASTSymbol sym } = do
let val = M.lookup sym env
case val of
Just ast' -> return (env, ast')
Nothing -> throwL (astPos ast) $ "symbol " ++ sym ++ " not defined in environment"
evaluateSymbol _ ast = throwL (astPos ast) $ "unreachable: evaluateSymbol, ast: " ++ show ast
evaluate :: Env -> AST -> LContext (Env, AST)
evaluate env AST { astNode = fnc@(ASTFunctionCall args@(x:_)) } =
do config <- ask
when (configPrintCallStack config) $ liftIO $ putStrLn $ "fn call: " ++ show fnc
case astNode x of
ASTSymbol "\\" ->
evaluateFunctionDef env args
ASTSymbol "match" ->
evaluateMatch env args
ASTSymbol "let" ->
evaluateLet env args
ASTSymbol "env" ->
evaluateEnv env args
_ ->
evaluateUserFunction env args
evaluate env ast@AST { astNode = (ASTSymbol _) } =
evaluateSymbol env ast
evaluate env ast@AST { astNode = (ASTVector vec) } =
do rets <- mapM (evaluate env) vec
let vec' = map snd rets
return $ (env, ast { astNode = ASTVector vec' })
evaluate env other =
return (env, other)
|
