Add with GADT support.
parent
7303a43f5b
commit
41926c8abc
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@ -1,4 +1,4 @@
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packages:
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initial-encoding
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leibniz-proof
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parser-closed
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parser-initial
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@ -0,0 +1,61 @@
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{-# LANGUAGE ExplicitForAll #-}
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{-# LANGUAGE FlexibleContexts #-}
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{-# LANGUAGE OverloadedStrings #-}
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module Main where
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import qualified Text.Megaparsec as M
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import Data.Bifunctor (first)
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import Data.Text (Text, pack)
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import Data.Text.IO (hGetContents)
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import Options.Applicative
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import Parser
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import System.Environment (getArgs)
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import System.IO (IOMode(ReadMode), openFile)
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data Args = Args
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{ argsFileName :: !FilePath
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, argsMethod :: !Text
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}
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args :: Parser Args
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args = Args
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<$> strArgument (metavar "FILENAME" <> help "The file we want to parse.")
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<*> strOption
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( short 'm'
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<> long "method"
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<> metavar "METHOD"
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<> showDefault
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<> value "naive"
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<> help "The parse strategy we want to try. Should be one of \
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\\"naive\", \"mul_pass\", or \"mem_cons\"."
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)
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runExpr :: (Text -> Either Text Expr) -> Text -> IO ()
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runExpr f input = case f input >>= eval of
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Right (EInt e) -> print e
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Right (EBool e) -> print e
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_ -> error "Could not evaluate expression fully."
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run :: Args -> IO ()
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run args = do
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handle <- openFile (argsFileName args) ReadMode
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contents <- hGetContents handle
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case argsMethod args of
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"naive" -> runExpr runNaive contents
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"mul_pass" -> runExpr runMulPass contents
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"mem_cons" -> runExpr runMemCons contents
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"gadt" -> case runGadt contents of
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Left e -> print e
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Right (Wrapper a) -> print $ gadtEval a
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_ -> error "Encountered an invalid parsing strategy."
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main :: IO ()
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main = run =<< execParser opts
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where
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opts = info (args <**> helper)
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( fullDesc
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<> progDesc "Different parsing strategies using initial encoding"
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<> header "Initial encoding parsing"
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)
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@ -1,13 +1,14 @@
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cabal-version: 3.4
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name: parser-initial
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name: initial-encoding
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version: 0.1.0.0
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executable parser-initial
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main-is: Main.hs
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build-depends: base ^>=4.14.3.0,
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initial-encoding,
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megaparsec,
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mtl,
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optparse-applicative,
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parser-initial,
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text,
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hs-source-dirs: app
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default-language: Haskell2010
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@ -32,8 +33,8 @@ test-suite parser-initial-test
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build-depends: base ^>=4.14.3.0,
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HUnit,
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hspec,
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initial-encoding,
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megaparsec,
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parser-initial,
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tasty,
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tasty-discover,
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tasty-hspec,
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@ -0,0 +1,311 @@
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{-# LANGUAGE BlockArguments #-}
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{-# LANGUAGE FlexibleContexts #-}
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{-# LANGUAGE GADTs #-}
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{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE RankNTypes #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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module Parser
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( Expr(..)
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, GExpr(..)
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, ParserT
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, Wrapper(..)
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, eval
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, gadtEval
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, gadtExpr
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, memConsExpr
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, mulPassExpr
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, naiveExpr
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, runGadt
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, runMemCons
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, runMulPass
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, runNaive
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) where
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import qualified Control.Monad.Combinators.Expr as E
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import qualified Text.Megaparsec as M
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import qualified Text.Megaparsec.Char as MC
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import qualified Text.Megaparsec.Char.Lexer as ML
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import Control.Applicative ((<|>))
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import Control.Applicative.Combinators (skipMany)
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import Control.DeepSeq (NFData(..), deepseq)
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import Control.Monad (join)
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import Control.Monad.Except (MonadError, throwError)
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import Control.Monad.State (MonadState, modify)
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import Control.Monad.Trans.Class (lift)
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import Control.Monad.Trans.Either (hoistEither)
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import Control.Monad.Trans.Except (ExceptT, runExceptT)
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import Data.Bifunctor (bimap, first)
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import Data.Char (isDigit)
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import Data.Foldable (foldl')
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import Data.Functor (($>), void)
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import Data.Maybe (isJust)
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import Data.Text (Text, pack, unpack)
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import Data.Text.IO (hGetContents)
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import Data.Void (Void)
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import Numeric (readDec)
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import System.Environment (getArgs)
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import System.IO (IOMode(ReadMode), openFile)
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-- ========================================
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-- ADT
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-- ========================================
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data Expr
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= EInt Integer
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| EBool Bool
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| EAdd Expr Expr
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| ESub Expr Expr
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| EAnd Expr Expr
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| EOr Expr Expr
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deriving (Eq, Show)
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eval :: Expr -> Either Text Expr
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eval e@(EInt _) = pure e
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eval e@(EBool _) = pure e
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eval (EAdd lhs rhs) = do
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(lhs', rhs') <- binInt lhs rhs
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pure $ EInt (lhs' + rhs')
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eval (ESub lhs rhs) = do
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(lhs', rhs') <- binInt lhs rhs
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pure $ EInt (lhs' - rhs')
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eval (EAnd lhs rhs) = do
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(lhs', rhs') <- binBool lhs rhs
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pure $ EBool (lhs' && rhs')
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eval (EOr lhs rhs) = do
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(lhs', rhs') <- binBool lhs rhs
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pure $ EBool (lhs' || rhs')
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binInt :: Expr -> Expr -> Either Text (Integer, Integer)
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binInt lhs rhs = do
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lhs' <- eval lhs
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rhs' <- eval rhs
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case (lhs', rhs') of
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(EInt lhs'', EInt rhs'') -> pure (lhs'', rhs'')
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_ -> Left "Expected two integers."
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binBool :: Expr -> Expr -> Either Text (Bool, Bool)
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binBool lhs rhs = do
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lhs' <- eval lhs
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rhs' <- eval rhs
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case (lhs', rhs') of
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(EBool lhs'', EBool rhs'') -> pure (lhs'', rhs'')
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_ -> Left "Expected two booleans."
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-- ========================================
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-- Lexers
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-- ========================================
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type ParserT = M.ParsecT Void Text
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space :: forall m. ParserT m ()
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space = ML.space MC.space1 M.empty M.empty
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{-# INLINE space #-}
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lexeme :: forall m a. ParserT m a -> ParserT m a
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lexeme = ML.lexeme MC.space
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{-# INLINE lexeme #-}
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symbol :: forall m. Text -> ParserT m Text
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symbol = ML.symbol space
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{-# INLINE symbol #-}
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parens :: forall m a. ParserT m a -> ParserT m a
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parens = M.between (symbol "(") (symbol ")")
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{-# INLINE parens #-}
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boolean :: forall m. ParserT m Bool
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boolean = lexeme $ MC.string "true" $> True <|> MC.string "false" $> False
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{-# INLINE boolean #-}
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integer :: forall m. ParserT m Integer
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integer = lexeme ML.decimal
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{-# INLINE integer #-}
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data Op = OpAdd | OpSub | OpAnd | OpOr
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ops :: forall m. ParserT m Op
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ops = M.choice
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[ symbol "+" $> OpAdd
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, symbol "-" $> OpSub
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, symbol "&&" $> OpAnd
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, symbol "||" $> OpOr
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]
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-- ========================================
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-- Naive attempt
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-- ========================================
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naiveExpr :: forall m. ParserT m Expr
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naiveExpr = E.makeExprParser term
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[ [binary "+" EAdd, binary "-" ESub]
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, [binary "&&" EAnd, binary "||" EOr]
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]
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where
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binary name f = E.InfixL (f <$ symbol name)
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term = parens naiveExpr <|>
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EInt <$> integer <|>
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EBool <$> boolean
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runNaive :: Text -> Either Text Expr
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runNaive input =
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let res = M.parse (naiveExpr <* M.eof) "" input
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in join $ bimap (pack . M.errorBundlePretty) eval res
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-- ========================================
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-- Multiple passes
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-- ========================================
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mulPassExpr :: forall m. MonadError Text m => ParserT m Expr
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mulPassExpr = expr >>= either (fail . unpack) pure
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where
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expr = E.makeExprParser term
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[ [ binary "+" binInt EInt EAdd
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, binary "-" binInt EInt ESub
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]
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, [ binary "&&" binBool EBool EAnd
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, binary "||" binBool EBool EOr
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]
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]
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binary name cast f bin = E.InfixL do
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void $ symbol name
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pure $ \lhs rhs -> do
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lhs' <- lhs
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rhs' <- rhs
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(lhs', rhs') <- cast lhs' rhs'
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k <- eval $ bin (f lhs') (f rhs')
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pure $ k `deepseq` k
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term = parens expr <|>
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Right . EInt <$> integer <|>
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Right . EBool <$> boolean
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runMulPass :: Text -> Either Text Expr
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runMulPass input =
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let res = M.runParserT (mulPassExpr <* M.eof) "" input
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in res >>= join . bimap (pack . M.errorBundlePretty) eval
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-- ========================================
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-- Memory consumption
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-- ========================================
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instance NFData Expr where
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rnf (EInt e) = rnf e
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rnf (EBool e) = rnf e
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rnf (EAdd lhs rhs) = rnf lhs `seq` rnf rhs
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rnf (ESub lhs rhs) = rnf lhs `seq` rnf rhs
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rnf (EAnd lhs rhs) = rnf lhs `seq` rnf rhs
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rnf (EOr lhs rhs) = rnf lhs `seq` rnf rhs
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memConsExpr :: forall m. MonadError Text m => ParserT m Expr
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memConsExpr = term >>= expr
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where
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expr t = do
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op <- M.option Nothing $ Just <$> ops
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case op of
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Just OpAdd -> nest t EAdd
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Just OpSub -> nest t ESub
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Just OpAnd -> nest t EAnd
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Just OpOr -> nest t EOr
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_ -> pure t
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nest :: Expr -> (Expr -> Expr -> Expr) -> ParserT m Expr
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nest t bin = do
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t' <- term
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case eval (bin t t') of
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Left e -> throwError e
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Right a -> a `deepseq` expr a
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term = do
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p <- M.option Nothing $ Just <$> symbol "("
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if isJust p then (term >>= expr) <* symbol ")" else
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EInt <$> integer <|> EBool <$> boolean
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runMemCons :: Text -> Either Text Expr
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runMemCons input =
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let res = M.runParserT (memConsExpr <* M.eof) "" input
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in res >>= join . bimap (pack . M.errorBundlePretty) eval
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-- ========================================
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-- GADTs
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-- ========================================
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data GExpr a where
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GInt :: Integer -> GExpr Integer
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GBool :: Bool -> GExpr Bool
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GAdd :: GExpr Integer -> GExpr Integer -> GExpr Integer
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GSub :: GExpr Integer -> GExpr Integer -> GExpr Integer
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GAnd :: GExpr Bool -> GExpr Bool -> GExpr Bool
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GOr :: GExpr Bool -> GExpr Bool -> GExpr Bool
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instance NFData (GExpr a) where
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rnf (GInt e) = rnf e
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rnf (GBool e) = rnf e
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rnf (GAdd lhs rhs) = rnf lhs `seq` rnf rhs
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rnf (GSub lhs rhs) = rnf lhs `seq` rnf rhs
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rnf (GAnd lhs rhs) = rnf lhs `seq` rnf rhs
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rnf (GOr lhs rhs) = rnf lhs `seq` rnf rhs
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data Wrapper = forall a. Show a => Wrapper (GExpr a)
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fromInt :: GExpr a -> Either Text (GExpr Integer)
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fromInt a@(GInt _ ) = pure a
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fromInt a@(GAdd _ _) = pure a
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fromInt a@(GSub _ _) = pure a
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fromInt _ = Left "Expected an integer type."
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fromBool :: GExpr a -> Either Text (GExpr Bool)
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fromBool a@(GBool _ ) = pure a
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fromBool a@(GAnd _ _) = pure a
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fromBool a@(GOr _ _) = pure a
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fromBool _ = Left "Expected a boolean type."
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gadtEval :: GExpr a -> a
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gadtEval (GInt a) = a
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gadtEval (GBool a) = a
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gadtEval (GAdd lhs rhs) = gadtEval lhs + gadtEval rhs
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gadtEval (GSub lhs rhs) = gadtEval lhs - gadtEval rhs
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gadtEval (GAnd lhs rhs) = gadtEval lhs && gadtEval rhs
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gadtEval (GOr lhs rhs) = gadtEval lhs || gadtEval rhs
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gadtExpr :: forall m. MonadError Text m => ParserT m Wrapper
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gadtExpr = term >>= expr
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where
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expr t = do
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op <- M.option Nothing $ Just <$> ops
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case op of
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Just OpAdd -> nest t fromInt GAdd GInt
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Just OpSub -> nest t fromInt GSub GInt
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Just OpAnd -> nest t fromBool GAnd GBool
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Just OpOr -> nest t fromBool GOr GBool
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_ -> pure t
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nest
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:: forall b
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. Show b
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=> Wrapper
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-> (forall a. GExpr a -> Either Text (GExpr b))
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-> (GExpr b -> GExpr b -> GExpr b)
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-> (b -> GExpr b)
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-> ParserT m Wrapper
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nest (Wrapper t) cast bin f = do
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Wrapper t' <- term
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case (cast t, cast t') of
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(Right lhs, Right rhs) -> do
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let z = f . gadtEval $ bin lhs rhs
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z `deepseq` expr (Wrapper z)
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(Left e, _) -> throwError e
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(_, Left e) -> throwError e
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term = do
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p <- M.option Nothing $ Just <$> symbol "("
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if isJust p then (term >>= expr) <* symbol ")" else
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Wrapper . GInt <$> integer <|> Wrapper . GBool <$> boolean
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runGadt :: Text -> Either Text Wrapper
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runGadt input =
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let res = M.runParserT (gadtExpr <* M.eof) "" input
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in res >>= first (pack . M.errorBundlePretty)
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@ -1,5 +1,6 @@
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{-# LANGUAGE BlockArguments #-}
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{-# LANGUAGE ExplicitForAll #-}
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{-# LANGUAGE GADTs #-}
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{-# LANGUAGE OverloadedStrings #-}
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module Test.ParserTest
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@ -8,18 +9,28 @@ module Test.ParserTest
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import qualified Text.Megaparsec as M
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import Data.Bifunctor (first)
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import Data.Functor.Identity (Identity(..))
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import Data.Text (Text, pack)
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import Parser
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import Test.Hspec (Expectation, Spec, describe, it, shouldBe)
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runParser :: Parser Expr -> Text -> IO (Either Text Expr)
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runParser m input = pure case M.parse (m <* M.eof) "ParserTest" input of
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Left e -> Left . pack $ M.errorBundlePretty e
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Right a -> eval a
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type Parser = ParserT Identity
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runParsers :: Text -> IO [Either Text Expr]
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runParsers input =
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mapM (`runParser` input) [naiveExpr, mulPassExpr, memConsExpr]
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convert :: GExpr a -> Expr
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convert (GInt a) = EInt a
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convert (GBool a) = EBool a
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convert (GAdd lhs rhs) = EAdd (convert lhs) (convert rhs)
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convert (GSub lhs rhs) = ESub (convert lhs) (convert rhs)
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convert (GAnd lhs rhs) = EAnd (convert lhs) (convert rhs)
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convert (GOr lhs rhs) = EOr (convert lhs) (convert rhs)
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runParsers :: Text -> [Either Text Expr]
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runParsers input = [runNaive, runMulPass, runMemCons, runGadt'] <*> [input]
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where
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runGadt' i = do
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Wrapper res <- runGadt i
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pure $ convert res
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allEqual :: forall a. Eq a => [a] -> Bool
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allEqual [] = True
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@ -29,13 +40,13 @@ allEqual (x:y:xs) = x == y && allEqual (y : xs)
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shouldParse :: Text -> Expr -> Expectation
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shouldParse input expected = do
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res@(x : _) <- runParsers input
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let res@(x : _) = runParsers input
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shouldBe x $ Right expected
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shouldBe True $ allEqual res
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shouldNotParse :: Text -> Text -> Expectation
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shouldNotParse input expected = do
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res@(x : _) <- runParsers input
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let res@(x : _) = runParsers input
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shouldBe x $ Left expected
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spec_parser :: Spec
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@ -1,52 +0,0 @@
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{-# LANGUAGE OverloadedStrings #-}
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module Main where
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import qualified Parser as P
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import qualified Text.Megaparsec as M
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import Data.Text (Text)
|
||||
import Data.Text.IO (hGetContents)
|
||||
import Options.Applicative
|
||||
import System.Environment (getArgs)
|
||||
import System.IO (IOMode(ReadMode), openFile)
|
||||
|
||||
data Args = Args
|
||||
{ argsFileName :: !FilePath
|
||||
, argsMethod :: !Text
|
||||
}
|
||||
|
||||
args :: Parser Args
|
||||
args = Args
|
||||
<$> strArgument (metavar "FILENAME" <> help "The file we want to parse.")
|
||||
<*> strOption
|
||||
( short 'm'
|
||||
<> long "method"
|
||||
<> metavar "METHOD"
|
||||
<> showDefault
|
||||
<> value "naive"
|
||||
<> help "The parse strategy we want to try. Should be one of \
|
||||
\\"naive\", \"mul_pass\", or \"mem_cons\"."
|
||||
)
|
||||
|
||||
run :: Args -> IO ()
|
||||
run args = do
|
||||
let method = case argsMethod args of
|
||||
"naive" -> P.naiveExpr
|
||||
"mul_pass" -> P.mulPassExpr
|
||||
"mem_cons" -> P.memConsExpr
|
||||
_ -> error "Encountered an invalid parsing strategy."
|
||||
handle <- openFile (argsFileName args) ReadMode
|
||||
contents <- hGetContents handle
|
||||
case M.parse (method <* M.eof) (argsFileName args) contents of
|
||||
Left e -> print $ M.errorBundlePretty e
|
||||
Right a -> print $ P.eval a
|
||||
|
||||
main :: IO ()
|
||||
main = run =<< execParser opts
|
||||
where
|
||||
opts = info (args <**> helper)
|
||||
( fullDesc
|
||||
<> progDesc "Different parsing strategies using initial encoding"
|
||||
<> header "Initial encoding parsing"
|
||||
)
|
||||
|
|
@ -1,188 +0,0 @@
|
|||
{-# LANGUAGE BlockArguments #-}
|
||||
{-# LANGUAGE ExplicitForAll #-}
|
||||
{-# LANGUAGE OverloadedStrings #-}
|
||||
|
||||
module Parser
|
||||
( Expr(..)
|
||||
, Parser
|
||||
, eval
|
||||
, memConsExpr
|
||||
, mulPassExpr
|
||||
, naiveExpr
|
||||
) where
|
||||
|
||||
import qualified Control.Monad.Combinators.Expr as E
|
||||
import qualified Text.Megaparsec as M
|
||||
import qualified Text.Megaparsec.Char as MC
|
||||
import qualified Text.Megaparsec.Char.Lexer as ML
|
||||
|
||||
import Control.Applicative ((<|>))
|
||||
import Control.DeepSeq (NFData(..), deepseq)
|
||||
import Control.Monad.State (MonadState, modify)
|
||||
import Control.Monad.Trans.Class (lift)
|
||||
import Control.Monad.Trans.Either (hoistEither)
|
||||
import Control.Monad.Trans.Except (ExceptT, runExceptT)
|
||||
import Data.Char (isDigit)
|
||||
import Data.Foldable (foldl')
|
||||
import Data.Functor (($>), void)
|
||||
import Data.Maybe (isJust)
|
||||
import Data.Text (Text, unpack)
|
||||
import Data.Text.IO (hGetContents)
|
||||
import Data.Void (Void)
|
||||
import Numeric (readDec)
|
||||
import System.Environment (getArgs)
|
||||
import System.IO (IOMode(ReadMode), openFile)
|
||||
|
||||
-- ========================================
|
||||
-- ADT
|
||||
-- ========================================
|
||||
|
||||
data Expr
|
||||
= EInt Integer
|
||||
| EBool Bool
|
||||
| EAdd Expr Expr
|
||||
| ESub Expr Expr
|
||||
| EAnd Expr Expr
|
||||
| EOr Expr Expr
|
||||
deriving (Eq, Show)
|
||||
|
||||
eval :: Expr -> Either Text Expr
|
||||
eval e@(EInt _) = pure e
|
||||
eval e@(EBool _) = pure e
|
||||
eval (EAdd lhs rhs) = do
|
||||
(lhs', rhs') <- binInt lhs rhs
|
||||
pure $ EInt (lhs' + rhs')
|
||||
eval (ESub lhs rhs) = do
|
||||
(lhs', rhs') <- binInt lhs rhs
|
||||
pure $ EInt (lhs' - rhs')
|
||||
eval (EAnd lhs rhs) = do
|
||||
(lhs', rhs') <- binBool lhs rhs
|
||||
pure $ EBool (lhs' && rhs')
|
||||
eval (EOr lhs rhs) = do
|
||||
(lhs', rhs') <- binBool lhs rhs
|
||||
pure $ EBool (lhs' || rhs')
|
||||
|
||||
binInt :: Expr -> Expr -> Either Text (Integer, Integer)
|
||||
binInt lhs rhs = do
|
||||
lhs' <- eval lhs
|
||||
rhs' <- eval rhs
|
||||
case (lhs', rhs') of
|
||||
(EInt lhs'', EInt rhs'') -> pure (lhs'', rhs'')
|
||||
_ -> Left "Expected two integers."
|
||||
|
||||
binBool :: Expr -> Expr -> Either Text (Bool, Bool)
|
||||
binBool lhs rhs = do
|
||||
lhs' <- eval lhs
|
||||
rhs' <- eval rhs
|
||||
case (lhs', rhs') of
|
||||
(EBool lhs'', EBool rhs'') -> pure (lhs'', rhs'')
|
||||
_ -> Left "Expected two booleans."
|
||||
|
||||
-- ========================================
|
||||
-- Lexers
|
||||
-- ========================================
|
||||
|
||||
type Parser = M.Parsec Void Text
|
||||
|
||||
space :: Parser ()
|
||||
space = ML.space MC.space1 M.empty M.empty
|
||||
{-# INLINE space #-}
|
||||
|
||||
lexeme :: forall a. Parser a -> Parser a
|
||||
lexeme = ML.lexeme MC.space
|
||||
{-# INLINE lexeme #-}
|
||||
|
||||
symbol :: Text -> Parser Text
|
||||
symbol = ML.symbol space
|
||||
{-# INLINE symbol #-}
|
||||
|
||||
parens :: forall a. Parser a -> Parser a
|
||||
parens = M.between (symbol "(") (symbol ")")
|
||||
{-# INLINE parens #-}
|
||||
|
||||
boolean :: Parser Bool
|
||||
boolean = lexeme $ MC.string "true" $> True <|> MC.string "false" $> False
|
||||
{-# INLINE boolean #-}
|
||||
|
||||
integer :: Parser Integer
|
||||
integer = lexeme ML.decimal
|
||||
{-# INLINE integer #-}
|
||||
|
||||
-- ========================================
|
||||
-- Naive attempt
|
||||
-- ========================================
|
||||
|
||||
naiveExpr :: Parser Expr
|
||||
naiveExpr = E.makeExprParser term
|
||||
[ [binary "+" EAdd, binary "-" ESub]
|
||||
, [binary "&&" EAnd, binary "||" EOr]
|
||||
]
|
||||
where
|
||||
binary name f = E.InfixL (f <$ symbol name)
|
||||
|
||||
term = parens naiveExpr <|>
|
||||
EInt <$> integer <|>
|
||||
EBool <$> boolean
|
||||
|
||||
-- ========================================
|
||||
-- Multiple passes
|
||||
-- ========================================
|
||||
|
||||
mulPassExpr :: Parser Expr
|
||||
mulPassExpr = expr >>= either (fail . unpack) pure
|
||||
where
|
||||
expr = E.makeExprParser term
|
||||
[ [binary "+" binInt EInt EAdd, binary "-" binInt EInt ESub]
|
||||
, [binary "&&" binBool EBool EAnd, binary "||" binBool EBool EOr]
|
||||
]
|
||||
|
||||
binary name b f op = E.InfixL do
|
||||
void $ symbol name
|
||||
pure $ \lhs rhs -> do
|
||||
lhs' <- lhs
|
||||
rhs' <- rhs
|
||||
(lhs', rhs') <- b lhs' rhs'
|
||||
eval $ op (f lhs') (f rhs')
|
||||
|
||||
term = parens expr <|>
|
||||
Right . EInt <$> integer <|>
|
||||
Right . EBool <$> boolean
|
||||
|
||||
-- ========================================
|
||||
-- Memory consumption
|
||||
-- ========================================
|
||||
|
||||
instance NFData Expr where
|
||||
rnf (EInt e) = rnf e
|
||||
rnf (EBool e) = rnf e
|
||||
rnf (EAdd lhs rhs) = rnf lhs `seq` rnf rhs
|
||||
rnf (ESub lhs rhs) = rnf lhs `seq` rnf rhs
|
||||
rnf (EAnd lhs rhs) = rnf lhs `seq` rnf rhs
|
||||
rnf (EOr lhs rhs) = rnf lhs `seq` rnf rhs
|
||||
|
||||
memConsExpr :: Parser Expr
|
||||
memConsExpr = do
|
||||
e <- runExceptT $ term >>= expr
|
||||
either (fail . unpack) pure e
|
||||
where
|
||||
expr :: Expr -> ExceptT Text Parser Expr
|
||||
expr t = do
|
||||
op <- lift $ M.option Nothing $ Just <$> M.choice
|
||||
[symbol "+", symbol "-", symbol "&&", symbol "||"]
|
||||
case op of
|
||||
Just "+" -> nest t EAdd
|
||||
Just "-" -> nest t ESub
|
||||
Just "&&" -> nest t EAnd
|
||||
Just "||" -> nest t EOr
|
||||
_ -> pure t
|
||||
|
||||
nest t f = do
|
||||
t' <- term
|
||||
z <- hoistEither . eval $ f t t'
|
||||
-- Need to reduce to NF for strictness guarantees.
|
||||
z `deepseq` expr z
|
||||
|
||||
term = do
|
||||
p <- lift $ M.option Nothing $ Just <$> symbol "("
|
||||
if isJust p then (term >>= expr) <* lift (symbol ")") else
|
||||
lift $ EInt <$> integer <|> EBool <$> boolean
|
||||
Loading…
Reference in New Issue