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|
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Language.Bs.Expr where
import Data.String (String)
import Data.Text (Text)
import qualified Data.Text as T
import GHC.Show
import Protolude hiding (show)
import qualified Text.PrettyPrint.Leijen.Text as PP
import Text.PrettyPrint.Leijen.Text hiding ((<$>))
type Ctx = Map Text Expr
data Env = Env { env :: Ctx, fenv :: Ctx }
deriving (Eq)
newtype Eval a = Eval { unEval :: ReaderT Env IO a }
deriving (Monad, Functor, Applicative, MonadReader Env, MonadIO)
data IFunc = IFunc { fn :: [Expr] -> Eval Expr }
deriving (Typeable)
instance Eq IFunc where
(==) _ _ = False
data Expr
= Atom Text
| List [Expr]
| Numb Integer
| Tape Text
| IFun IFunc -- TODO: call this Kern
| Func IFunc Env
| Bool Bool
| Nil
deriving (Typeable, Eq)
instance Show Expr where
show = T.unpack . ppexpr
data LispErrorType
= NumArgs Integer [Expr]
| LengthOfList Text Int
| ExpectedList Text
| ParseError String
| TypeMismatch Text Expr
| BadSpecialForm Text
| NotFunction Expr
| UnboundVar Text
| Default Expr
| ReadFileError Text
deriving (Typeable)
data LispError = LispError Expr LispErrorType
instance Show LispErrorType where
show = T.unpack . ppexpr
instance Show LispError where
show = T.unpack . ppexpr
instance Exception LispErrorType
instance Exception LispError
ppexpr :: Pretty a => a -> Text
ppexpr x = PP.displayTStrict (PP.renderPretty 1.0 70 (pretty x))
--prettyList :: [Doc] -> Doc
--prettyList = encloseSep lparen rparen PP.space
instance Pretty Expr where
pretty v =
case v of
Atom a ->
textStrict a
List ls ->
prettyList $ fmap pretty ls
Numb n ->
integer n
Tape t ->
textStrict "\"" <> textStrict t <> textStrict "\""
IFun _ ->
textStrict "<internal function>"
Func _ _ ->
textStrict "<lambda function>"
Bool True ->
textStrict "#t"
Bool False ->
textStrict "#f"
Nil ->
textStrict "'()"
instance Pretty LispErrorType where
pretty err = case err of
NumArgs i args ->
textStrict "number of arguments"
<$$> textStrict "expected"
<+> textStrict (T.pack $ show i)
<$$> textStrict "received"
<+> textStrict (T.pack $ show $ length args)
LengthOfList txt i ->
textStrict "length of list in:"
<+> textStrict txt
<$$> textStrict "length:"
<+> textStrict (T.pack $ show i)
ParseError txt ->
textStrict "cannot parse expr:"
<+> textStrict (T.pack txt)
TypeMismatch txt expr ->
textStrict "type mismatch:"
<$$> textStrict txt
<$$> pretty expr
BadSpecialForm txt ->
textStrict "bad special form:"
<$$> textStrict txt
NotFunction expr ->
textStrict "not a function"
<$$> pretty expr
UnboundVar txt ->
textStrict "unbound variable:"
<$$> textStrict txt
Default _ ->
textStrict "default error"
ReadFileError txt ->
textStrict "error reading file:"
<$$> textStrict txt
ExpectedList txt ->
textStrict "expected list:"
<$$> textStrict txt
instance Pretty LispError where
pretty (LispError expr typ) =
textStrict "error evaluating:"
<$$> indent 4 (pretty expr)
<$$> pretty typ
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