The io-streams library contains simple and easy-to-use primitives for I/O using
streams. Most users will want to import the top-level convenience module
"System.IO.Streams", which re-exports most of the library:
' import System.IO.Streams (InputStream, OutputStream) import qualified
System.IO.Streams as Streams '
For first-time users, 'io-streams' comes with an included tutorial, which can
be found in the "System.IO.Streams.Tutorial" module.
The 'io-streams' user API has two basic types: 'InputStream a' and
'OutputStream a', and three fundamental I/O primitives:
' -- read an item from an input stream Streams.read :: InputStream a -> IO
-- push an item back to an input stream Streams.unRead :: a -> InputStream a ->
-- write to an output stream Streams.write :: Maybe a -> OutputStream a -> IO
Streams can be transformed by composition and hooked together with provided
' ghci> Streams.fromList [1,2,3::Int] >>= Streams.map (*10) >>= Streams.toList
Stream composition leaves the original stream accessible:
' ghci> input <- Streams.fromByteString "long string" ghci> wrapped <-
Streams.takeBytes 4 input ghci> Streams.read wrapped Just "long" ghci>
Streams.read wrapped Nothing ghci> Streams.read input Just " string" '
Simple types and operations in the IO monad mean straightforward and simple
exception handling and resource cleanup using Haskell standard library
facilities like 'Control.Exception.bracket'.
'io-streams' comes with:
- functions to use files, handles, concurrent channels, sockets, lists,
vectors, and more as streams.
- a variety of combinators for wrapping and transforming streams, including
compression and decompression using zlib, controlling precisely how many bytes
are read from or written to a stream, buffering output using bytestring
builders, folds, maps, filters, zips, etc.