hw-polysemy-0.2.14.0: Opinionated polysemy library
Safe HaskellSafe-Inferred
LanguageHaskell2010

HaskellWorks.Polysemy.System.IO

Synopsis

Documentation

data BufferMode #

Three kinds of buffering are supported: line-buffering, block-buffering or no-buffering. These modes have the following effects. For output, items are written out, or flushed, from the internal buffer according to the buffer mode:

  • line-buffering: the entire output buffer is flushed whenever a newline is output, the buffer overflows, a hFlush is issued, or the handle is closed.
  • block-buffering: the entire buffer is written out whenever it overflows, a hFlush is issued, or the handle is closed.
  • no-buffering: output is written immediately, and never stored in the buffer.

An implementation is free to flush the buffer more frequently, but not less frequently, than specified above. The output buffer is emptied as soon as it has been written out.

Similarly, input occurs according to the buffer mode for the handle:

  • line-buffering: when the buffer for the handle is not empty, the next item is obtained from the buffer; otherwise, when the buffer is empty, characters up to and including the next newline character are read into the buffer. No characters are available until the newline character is available or the buffer is full.
  • block-buffering: when the buffer for the handle becomes empty, the next block of data is read into the buffer.
  • no-buffering: the next input item is read and returned. The hLookAhead operation implies that even a no-buffered handle may require a one-character buffer.

The default buffering mode when a handle is opened is implementation-dependent and may depend on the file system object which is attached to that handle. For most implementations, physical files will normally be block-buffered and terminals will normally be line-buffered.

Constructors

NoBuffering

buffering is disabled if possible.

LineBuffering

line-buffering should be enabled if possible.

BlockBuffering (Maybe Int)

block-buffering should be enabled if possible. The size of the buffer is n items if the argument is Just n and is otherwise implementation-dependent.

Instances

Instances details
Read BufferMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Handle.Types

Show BufferMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Handle.Types

Eq BufferMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Handle.Types

Ord BufferMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Handle.Types

type FilePath = String #

File and directory names are values of type String, whose precise meaning is operating system dependent. Files can be opened, yielding a handle which can then be used to operate on the contents of that file.

data Handle #

Haskell defines operations to read and write characters from and to files, represented by values of type Handle. Each value of this type is a handle: a record used by the Haskell run-time system to manage I/O with file system objects. A handle has at least the following properties:

  • whether it manages input or output or both;
  • whether it is open, closed or semi-closed;
  • whether the object is seekable;
  • whether buffering is disabled, or enabled on a line or block basis;
  • a buffer (whose length may be zero).

Most handles will also have a current I/O position indicating where the next input or output operation will occur. A handle is readable if it manages only input or both input and output; likewise, it is writable if it manages only output or both input and output. A handle is open when first allocated. Once it is closed it can no longer be used for either input or output, though an implementation cannot re-use its storage while references remain to it. Handles are in the Show and Eq classes. The string produced by showing a handle is system dependent; it should include enough information to identify the handle for debugging. A handle is equal according to == only to itself; no attempt is made to compare the internal state of different handles for equality.

Instances

Instances details
Show Handle

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Handle.Types

Eq Handle

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Handle.Types

Methods

(==) :: Handle -> Handle -> Bool #

(/=) :: Handle -> Handle -> Bool #

data HandlePosn #

Instances

Instances details
Show HandlePosn

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Handle

Eq HandlePosn

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Handle

data IO a #

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.

Instances

Instances details
MonadFail IO

Since: base-4.9.0.0

Instance details

Defined in Control.Monad.Fail

Methods

fail :: String -> IO a #

MonadIO IO

Since: base-4.9.0.0

Instance details

Defined in Control.Monad.IO.Class

Methods

liftIO :: IO a -> IO a #

Alternative IO

Takes the first non-throwing IO action's result. empty throws an exception.

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

empty :: IO a #

(<|>) :: IO a -> IO a -> IO a #

some :: IO a -> IO [a] #

many :: IO a -> IO [a] #

Applicative IO

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

pure :: a -> IO a #

(<*>) :: IO (a -> b) -> IO a -> IO b #

liftA2 :: (a -> b -> c) -> IO a -> IO b -> IO c #

(*>) :: IO a -> IO b -> IO b #

(<*) :: IO a -> IO b -> IO a #

Functor IO

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

fmap :: (a -> b) -> IO a -> IO b #

(<$) :: a -> IO b -> IO a #

Monad IO

Since: base-2.1

Instance details

Defined in GHC.Base

Methods

(>>=) :: IO a -> (a -> IO b) -> IO b #

(>>) :: IO a -> IO b -> IO b #

return :: a -> IO a #

MonadPlus IO

Takes the first non-throwing IO action's result. mzero throws an exception.

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

mzero :: IO a #

mplus :: IO a -> IO a -> IO a #

MonadCatch IO 
Instance details

Defined in Control.Monad.Catch

Methods

catch :: (HasCallStack, Exception e) => IO a -> (e -> IO a) -> IO a #

MonadMask IO 
Instance details

Defined in Control.Monad.Catch

Methods

mask :: HasCallStack => ((forall a. IO a -> IO a) -> IO b) -> IO b #

uninterruptibleMask :: HasCallStack => ((forall a. IO a -> IO a) -> IO b) -> IO b #

generalBracket :: HasCallStack => IO a -> (a -> ExitCase b -> IO c) -> (a -> IO b) -> IO (b, c) #

MonadThrow IO 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: (HasCallStack, Exception e) => e -> IO a #

PrimBase IO 
Instance details

Defined in Control.Monad.Primitive

Methods

internal :: IO a -> State# (PrimState IO) -> (# State# (PrimState IO), a #) #

PrimMonad IO 
Instance details

Defined in Control.Monad.Primitive

Associated Types

type PrimState IO #

Methods

primitive :: (State# (PrimState IO) -> (# State# (PrimState IO), a #)) -> IO a #

Quasi IO 
Instance details

Defined in Language.Haskell.TH.Syntax

Quote IO 
Instance details

Defined in Language.Haskell.TH.Syntax

Methods

newName :: String -> IO Name #

MonadUnliftIO IO 
Instance details

Defined in Control.Monad.IO.Unlift

Methods

withRunInIO :: ((forall a. IO a -> IO a) -> IO b) -> IO b #

MonadError IOException IO 
Instance details

Defined in Control.Monad.Error.Class

Methods

throwError :: IOException -> IO a #

catchError :: IO a -> (IOException -> IO a) -> IO a #

Monoid a => Monoid (IO a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Base

Methods

mempty :: IO a #

mappend :: IO a -> IO a -> IO a #

mconcat :: [IO a] -> IO a #

Semigroup a => Semigroup (IO a)

Since: base-4.10.0.0

Instance details

Defined in GHC.Base

Methods

(<>) :: IO a -> IO a -> IO a #

sconcat :: NonEmpty (IO a) -> IO a #

stimes :: Integral b => b -> IO a -> IO a #

type PrimState IO 
Instance details

Defined in Control.Monad.Primitive

data IOMode #

Instances

Instances details
Enum IOMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.IOMode

Ix IOMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.IOMode

Read IOMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.IOMode

Show IOMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.IOMode

Eq IOMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.IOMode

Methods

(==) :: IOMode -> IOMode -> Bool #

(/=) :: IOMode -> IOMode -> Bool #

Ord IOMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.IOMode

data NewlineMode #

Specifies the translation, if any, of newline characters between internal Strings and the external file or stream. Haskell Strings are assumed to represent newlines with the '\n' character; the newline mode specifies how to translate '\n' on output, and what to translate into '\n' on input.

Constructors

NewlineMode 

Fields

Instances

Instances details
Read NewlineMode

Since: base-4.3.0.0

Instance details

Defined in GHC.IO.Handle.Types

Show NewlineMode

Since: base-4.3.0.0

Instance details

Defined in GHC.IO.Handle.Types

Eq NewlineMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Handle.Types

Ord NewlineMode

Since: base-4.3.0.0

Instance details

Defined in GHC.IO.Handle.Types

data SeekMode #

A mode that determines the effect of hSeek hdl mode i.

Constructors

AbsoluteSeek

the position of hdl is set to i.

RelativeSeek

the position of hdl is set to offset i from the current position.

SeekFromEnd

the position of hdl is set to offset i from the end of the file.

Instances

Instances details
Enum SeekMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Device

Ix SeekMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Device

Read SeekMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Device

Show SeekMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Device

Eq SeekMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Device

Ord SeekMode

Since: base-4.2.0.0

Instance details

Defined in GHC.IO.Device

data TextEncoding #

A TextEncoding is a specification of a conversion scheme between sequences of bytes and sequences of Unicode characters.

For example, UTF-8 is an encoding of Unicode characters into a sequence of bytes. The TextEncoding for UTF-8 is utf8.

Instances

Instances details
Show TextEncoding

Since: base-4.3.0.0

Instance details

Defined in GHC.IO.Encoding.Types

type String = [Char] #

A String is a list of characters. String constants in Haskell are values of type String.

See Data.List for operations on lists.

withFile :: HasCallStack => Member (Error IOException) r => Member (Embed IO) r => Member Resource r => Member Log r => FilePath -> IOMode -> (Handle -> Sem r a) -> Sem r a Source #

Open a file handle and run an action, closing the handle when done.

hClose :: HasCallStack => Member (Error IOException) r => Member (Embed IO) r => Member Log r => Handle -> Sem r () Source #

Close the file handle.

openFile :: HasCallStack => Member (Error IOException) r => Member (Embed IO) r => Member Log r => FilePath -> IOMode -> Sem r Handle Source #

Open a file handle.

readFile :: HasCallStack => Member (Error IOException) r => Member (Embed IO) r => Member Log r => FilePath -> Sem r String Source #

Read a file as a string.

withBinaryFile :: HasCallStack => Member (Error IOException) r => Member (Embed IO) r => Member Resource r => Member Log r => FilePath -> IOMode -> (Handle -> Sem r a) -> Sem r a Source #

Open a file handle and run an action, closing the handle when done.

openBinaryFile :: HasCallStack => Member (Error IOException) r => Member (Embed IO) r => Member Log r => FilePath -> IOMode -> Sem r Handle Source #

Open a file handle.

latin1 :: TextEncoding #

The Latin1 (ISO8859-1) encoding. This encoding maps bytes directly to the first 256 Unicode code points, and is thus not a complete Unicode encoding. An attempt to write a character greater than '\255' to a Handle using the latin1 encoding will result in an error.

utf8 :: TextEncoding #

The UTF-8 Unicode encoding

utf8_bom :: TextEncoding #

The UTF-8 Unicode encoding, with a byte-order-mark (BOM; the byte sequence 0xEF 0xBB 0xBF). This encoding behaves like utf8, except that on input, the BOM sequence is ignored at the beginning of the stream, and on output, the BOM sequence is prepended.

The byte-order-mark is strictly unnecessary in UTF-8, but is sometimes used to identify the encoding of a file.

utf16 :: TextEncoding #

The UTF-16 Unicode encoding (a byte-order-mark should be used to indicate endianness).

utf16le :: TextEncoding #

The UTF-16 Unicode encoding (little-endian)

utf16be :: TextEncoding #

The UTF-16 Unicode encoding (big-endian)

utf32 :: TextEncoding #

The UTF-32 Unicode encoding (a byte-order-mark should be used to indicate endianness).

utf32le :: TextEncoding #

The UTF-32 Unicode encoding (little-endian)

utf32be :: TextEncoding #

The UTF-32 Unicode encoding (big-endian)

localeEncoding :: TextEncoding #

The Unicode encoding of the current locale

This is the initial locale encoding: if it has been subsequently changed by setLocaleEncoding this value will not reflect that change.

char8 :: TextEncoding #

An encoding in which Unicode code points are translated to bytes by taking the code point modulo 256. When decoding, bytes are translated directly into the equivalent code point.

This encoding never fails in either direction. However, encoding discards information, so encode followed by decode is not the identity.

Since: base-4.4.0.0

nativeNewline :: Newline #

The native newline representation for the current platform: LF on Unix systems, CRLF on Windows.

noNewlineTranslation :: NewlineMode #

Do no newline translation at all.

noNewlineTranslation  = NewlineMode { inputNL  = LF, outputNL = LF }

universalNewlineMode :: NewlineMode #

Map '\r\n' into '\n' on input, and '\n' to the native newline representation on output. This mode can be used on any platform, and works with text files using any newline convention. The downside is that readFile >>= writeFile might yield a different file.

universalNewlineMode  = NewlineMode { inputNL  = CRLF,
                                      outputNL = nativeNewline }

nativeNewlineMode :: NewlineMode #

Use the native newline representation on both input and output

nativeNewlineMode  = NewlineMode { inputNL  = nativeNewline
                                   outputNL = nativeNewline }