Added fileRead and fileWrite

src/Turtle.hs

@@ -2,6 +2,7 @@ module Turtle (
     -- * Shell
       Shell
     , fold
+    , foldIO
     , runShell
 
     -- * Utilities

src/Turtle/Shell.hs

@@ -12,13 +12,18 @@
 module Turtle.Shell (
       Shell(..)
     , fold
+    , foldIO
     , runShell
+
+    -- * Re-exports
+    , Fold(..)
+    , FoldM(..)
     ) where
 
 import Control.Applicative (Applicative(..), Alternative(..), liftA2)
 import Control.Monad (MonadPlus(..), ap)
 import Control.Monad.IO.Class (MonadIO(..))
-import Control.Foldl (Fold)
+import Control.Foldl (Fold, FoldM)
 import qualified Control.Foldl as Foldl
 import Data.Monoid (Monoid(..))
 import Data.String (IsString(..))
@@ -28,7 +33,10 @@ newtype Shell a = Shell
     { foldM_ :: forall r x . (x -> a -> IO x) -> IO x -> (x -> IO r) -> IO r }
 
 fold :: Fold a b -> Shell a -> IO b
-fold f s = Foldl.impurely (foldM_ s) (Foldl.generalize f)
+fold f = foldIO (Foldl.generalize f)
+
+foldIO :: FoldM IO a b -> Shell a -> IO b
+foldIO f s = Foldl.impurely (foldM_ s) f
 
 runShell :: Shell a -> IO ()
 runShell = fold (pure ())

src/Turtle/Util.hs

@@ -2,7 +2,11 @@ module Turtle.Util where
 
 import Control.Applicative (Alternative(..))
 
+import Control.Exception (bracket)
 import Control.Monad (guard)
+import qualified Data.Text.IO as Text
+import System.IO
+
 import Turtle.Parser
 import Turtle.Shell
 
@@ -18,3 +22,25 @@ grep p s = do
     str <- s
     guard (not (null (parse p str)))
     return str
+
+fileRead :: FilePath -> Shell Text
+fileRead file = Shell (\step begin done -> do
+    x0 <- begin
+    x1 <- bracket (openFile file ReadMode) hClose (\handle -> do
+        let go x = do
+                eof <- hIsEOF handle
+                if eof
+                    then return x
+                    else do
+                        str <- Text.hGetLine handle
+                        x'  <- step x str
+                        go x'
+        go x0 )
+    done x1 )
+
+fileWrite :: FilePath -> FoldM IO Text ()
+fileWrite file = FoldM step (openFile file WriteMode) hClose
+  where
+    step handle txt = do
+        Text.hPutStrLn handle txt
+        return handle