Module "IO.curry"

Library for IO operations like reading and writing files that are not already contained in the prelude.

Author: Michael Hanus, Bernd Brassel

Version: June 2006

Datatypes:
Handle | IOMode | SeekMode

Constructors:
AbsoluteSeek | AppendMode | ReadMode | RelativeSeek | SeekFromEnd | WriteMode

Functions:
getContents | hClose | hFlush | hGetChar | hGetContents | hGetLine | hIsEOF | hIsReadable | hIsWritable | hPrint | hPutChar | hPutStr | hPutStrLn | hReady | hSeek | hWaitForInput | hWaitForInputOrMsg | hWaitForInputs | hWaitForInputsOrMsg | isEOF | openFile | stderr | stdin | stdout

stdin  :: Handle              Standard input stream.

stdout  :: Handle              Standard output stream.

stderr  :: Handle              Standard error stream.

openFile  :: String -> IOMode -> IO Handle              Opens a file in specified mode and returns a handle to it.

hClose  :: Handle -> IO ()              Closes a file handle and flushes the buffer in case of output file.

hFlush  :: Handle -> IO ()              Flushes the buffer associated to handle in case of output file.

hIsEOF  :: Handle -> IO Bool              Is handle at end of file?

isEOF  :: IO Bool              Is standard input at end of file?

hSeek  :: Handle -> SeekMode -> Int -> IO ()              Set the position of a handle to a seekable stream (e.g., a file).

hWaitForInput  :: Handle -> Int -> IO Bool              Waits until input is available on the given handle.

hWaitForInputs  :: [Handle] -> Int -> IO Int              Waits until input is available on some of the given handles.

hWaitForInputOrMsg  :: Handle -> [a] -> IO (Either Handle [a])              Waits until input is available on a given handles or a message in the message stream.

hWaitForInputsOrMsg  :: [Handle] -> [a] -> IO (Either Int [a])              Waits until input is available on some of the given handles or a message in the message stream.

hReady  :: Handle -> IO Bool              Checks whether an input is available on a given handle.

hGetChar  :: Handle -> IO Char              Reads a character from an input handle and returns it.

hGetLine  :: Handle -> IO String              Reads a line from an input handle and returns it.

hGetContents  :: Handle -> IO String              Reads the complete contents from an input handle and closes the input handle before returning the contents.

getContents  :: IO String              Reads the complete contents from the standard input stream until EOF.

hPutChar  :: Handle -> Char -> IO ()              Puts a character to an output handle.

hPutStr  :: Handle -> String -> IO ()              Puts a string to an output handle.

hPutStrLn  :: Handle -> String -> IO ()              Puts a string with a newline to an output handle.

hPrint  :: Handle -> a -> IO ()              Converts a term into a string and puts it to an output handle.

hIsReadable  :: Handle -> IO Bool              Is the handle readable?

hIsWritable  :: Handle -> IO Bool              Is the handle writable?

Handle

The abstract type of a handle for a stream.

Constructors:

---

IOMode

The modes for opening a file.

Constructors:

ReadMode :: IOMode

WriteMode :: IOMode

AppendMode :: IOMode

---

SeekMode

The modes for positioning with hSeek in a file.

Constructors:

AbsoluteSeek :: SeekMode

RelativeSeek :: SeekMode

SeekFromEnd :: SeekMode

---

---

Exported functions:

---

stdin :: Handle   

Standard input stream.

Further infos:

• externally defined

---

stdout :: Handle   

Standard output stream.

Further infos:

• externally defined

---

stderr :: Handle   

Standard error stream.

Further infos:

• externally defined

---

openFile :: String -> IOMode -> IO Handle   

Opens a file in specified mode and returns a handle to it.

---

hClose :: Handle -> IO ()   

Closes a file handle and flushes the buffer in case of output file.

---

hFlush :: Handle -> IO ()   

Flushes the buffer associated to handle in case of output file.

---

hIsEOF :: Handle -> IO Bool   

Is handle at end of file?

---

isEOF :: IO Bool   

Is standard input at end of file?

---

hSeek :: Handle -> SeekMode -> Int -> IO ()   

Set the position of a handle to a seekable stream (e.g., a file). If the second argument is AbsoluteSeek, SeekFromEnd, or RelativeSeek, the position is set relative to the beginning of the file, to the end of the file, or to the current position, respectively.

---

hWaitForInput :: Handle -> Int -> IO Bool   

Waits until input is available on the given handle. If no input is available within t milliseconds, it returns False, otherwise it returns True.

Example call:  (hWaitForInput handle timeout)

Parameters:

handle - a handle for an input stream

timeout - milliseconds to wait for input (< 0 : no time out)

---

hWaitForInputs :: [Handle] -> Int -> IO Int   

Waits until input is available on some of the given handles. If no input is available within t milliseconds, it returns -1, otherwise it returns the index of the corresponding handle with the available data.

Example call:  (hWaitForInputs handles timeout)

Parameters:

handles - a list of handles for input streams

timeout - milliseconds to wait for input (< 0 : no time out)

Returns:

-1 if no input is available within the time out, otherwise i if (handles!!i) has data available

---

hWaitForInputOrMsg :: Handle -> [a] -> IO (Either Handle [a])   

Waits until input is available on a given handles or a message in the message stream. Usually, the message stream comes from an external port. Thus, this operation implements a committed choice over receiving input from an IO handle or an external port.
Note that the implementation of this operation works only with Sicstus-Prolog 3.8.5 or higher (due to a bug in previous versions of Sicstus-Prolog).

Example call:  (hWaitForInputOrMsg handle msgs)

Parameters:

handle - a handle for an input stream

msgs - a stream of messages received via an external port (see Ports)

Returns:

(Left handle) if the handle has some data available (Right msgs) if the stream msgs is instantiated with at least one new message at the head

---

hWaitForInputsOrMsg :: [Handle] -> [a] -> IO (Either Int [a])   

Waits until input is available on some of the given handles or a message in the message stream. Usually, the message stream comes from an external port. Thus, this operation implements a committed choice over receiving input from IO handles or an external port.
Note that the implementation of this operation works only with Sicstus-Prolog 3.8.5 or higher (due to a bug in previous versions of Sicstus-Prolog).

Example call:  (hWaitForInputsOrMsg handles msgs)

Parameters:

handles - a list of handles for input streams

msgs - a stream of messages received via an external port (see Ports)

Returns:

(Left i) if (handles!!i) has some data available (Right msgs) if the stream msgs is instantiated with at least one new message at the head

---

hReady :: Handle -> IO Bool   

Checks whether an input is available on a given handle.

---

hGetChar :: Handle -> IO Char   

Reads a character from an input handle and returns it.

---

hGetLine :: Handle -> IO String   

Reads a line from an input handle and returns it.

---

hGetContents :: Handle -> IO String   

Reads the complete contents from an input handle and closes the input handle before returning the contents.

---

getContents :: IO String   

Reads the complete contents from the standard input stream until EOF.

---

hPutChar :: Handle -> Char -> IO ()   

Puts a character to an output handle.

---

hPutStr :: Handle -> String -> IO ()   

Puts a string to an output handle.

---

hPutStrLn :: Handle -> String -> IO ()   

Puts a string with a newline to an output handle.

---

hPrint :: Handle -> a -> IO ()   

Converts a term into a string and puts it to an output handle.

---

hIsReadable :: Handle -> IO Bool   

Is the handle readable?

---

hIsWritable :: Handle -> IO Bool   

Is the handle writable?

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