Robert Rothenberg
I'm implementing a variant of Prolog in Haskell (yes, I know others already exist...) and am looking to solve the following issues:
(1) I need to translate anonymous variables "_" into unique variable names. Data.Unique does not give me a printable identifier. Is there another package that does this?
(2) Is there a cabal package similar to the Atom.hs module form ginsu, that associates strings with unique hashes?
The alternative of course is to maintain state variables and pass them along to display and parsing functions, but that makes it difficult to make the terms instances of Read/Show without reference to a global variable anyhow.
Well, you can use hashUnique, but there are no guarantees about collisions. If you need thread safety, the easiest approach is an id generator thread like this: idVar <- newEmptyMVar forkIO . mapM (putMVar idVar) $ [0..] let getId = takeMVar idVar If you don't need it, you will need to pass state around, just like with Data.Unique. Greets Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://blog.ertes.de/