Basic concepts

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/Postdelay/Utils.hs b/lib/Postdelay/Utils.hs
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+++ b/lib/Postdelay/Utils.hs
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+{-# LANGUAGE FlexibleContexts #-}
+
+module Postdelay.Utils
+  ( hoistParsecT
+  ) where
+
+import Control.Monad.Error.Class
+
+import Data.Functor
+import Data.Either
+
+import Data.Functor.Identity
+import Text.Parsec.Prim
+import Text.Parsec.Error
+
+hoistParsecT :: (Monad m, Stream s Identity t, Stream s m t) => ParsecT s u Identity a -> ParsecT s u m a
+hoistParsecT p = do
+  st <- getParserState
+  let res = runParser p' undefined "" undefined
+      p' = setParserState st >> ((,) <$> getState <*> p)
+  either (fail . show) (\(st', res) -> putState st' $> res) $ res