Abstract

ing away from the request and response lists. 10 Monadic style I/O operations can be implemented on top of synchronized streams in much the same way as CPS style I/O. A simple I/O monad (without error handling) is shown in Figure 5. In monadic style, the above example would look like this: main = doIO mainIO mainIO = readFileIO "forward" bindIO \ contents ® let revcontents = (unlines.reverse.lines) contents in writeFileIO "backward" revcontents) 2.3 Concurrency and GUI Programming We have seen above how you can use streams, continuations, or monads, to specify a sequence of I/O operations that the program should perform. For many purposes, a single sequence of I/O operations is an adequate description of the I/O behaviour of a program. But there are other cases. For programs that interact with several external entities (teletype terminals, other computers on a network, elements in a graphical user interface, robotic sensors/motors, etc.) there is usually no predetermined order in w...

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