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module Evaluator (eval) where
import Control.Monad.Except
import Environment
import Error.Base (LispError (..), LispResult (..),
unwrap)
import Operators
import Parser
import Text.ParserCombinators.Parsec
apply :: String -> [Expr] -> LispResult Expr
apply fn args = maybe
(throwError $ UnknownFunction fn)
($ args)
(lookup fn primitives)
eval :: Env -> Expr -> IOResult Expr
eval _ v@(StringLiteral s) = return v
eval _ v@(IntLiteral i) = return v
eval _ v@(BoolLiteral b) = return v
eval env (Id l) = getVar env l
eval _ v@(FloatLiteral f) = return v
eval env v@(Vector xs) = liftM Vector $ mapM (eval env) xs
eval env (List[Id "quote", val]) = return val
eval env (List[Id "quasiquote", val]) = undefined
eval env (List[Id "unquote", val]) = eval env val
eval env (List [Id "set!", Id var, val]) = do
e <- eval env val
setVar env var e
return e
eval env (List [Id "define", Id var, val]) = do
e <- eval env val
defineVar env var e
return e
eval env (List (Id fn : args)) = mapM (eval env) args >>= liftLispResult . apply fn
eval env NoReturn = throwError $ BadForm "Invalid usage of non-returning expression" NoReturn
-- handle bad forms
eval env invalidForm = throwError $ BadForm "lisk can't recognize this form" invalidForm
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