8 Aug
2013
8 Aug
'13
12:05 p.m.
On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
One could simply implement IO as a free monad Interesting. I wonder how.
See [1] for an explanation of free monads in general. For IO in particular, define a functor data IOF a = GetChar (Char -> a) | PutChar Char a | ... with constructors for all elementary IO operations. Then take type IO a = Free IOF a and define getChar :: IO Char getChar = liftF (GetChar id) putChar :: Char -> IO () putChar c = liftF (PutChar c ()) etc.. I make no claims about the performance of a runtime system based on suhc a representation! Tom