IO package:base-prelude

A value of type IO a is a computation which, when performed, does some I/O before returning a value of type a. There is really only one way to "perform" an I/O action: bind it to Main.main in your program. When your program is run, the I/O will be performed. It isn't possible to perform I/O from an arbitrary function, unless that function is itself in the IO monad and called at some point, directly or indirectly, from Main.main. IO is a monad, so IO actions can be combined using either the do-notation or the >> and >>= operations from the Monad class.

The Haskell 2010 type for exceptions in the IO monad. Any I/O operation may raise an IOException instead of returning a result. For a more general type of exception, including also those that arise in pure code, see Exception. In Haskell 2010, this is an opaque type.

An abstract type that contains a value for each variant of IOException.

Exceptions that occur in the IO monad. An IOException records a more specific error type, a descriptive string and maybe the handle that was used when the error was flagged.

See openFile

A mutable variable in the IO monad

Monoid under bitwise inclusive OR.

>>> getIor (Ior 0xab <> Ior 0x12) :: Word8
187

Raise an IOException in the IO monad.