I'm not convinced that the binary library should "natively" support cyclic data. I think that if saying:
print x
would not terminate, then there's no reason that
puts bh x
should terminate. I like to think of "puts" as a binary version of print. (That is, of course, unless the instance writer for the Binary/Show instances of the type of x is smart enough to not keep writing the same thing over and over again.) I would challenge the interested party to write a Show instance of String which wouldn't loop indefinitely on "repeat 'x'". well, it is your choice to think of it as you like, but this is not what my original mail was about. i think the ability to make data persistant is a useful one and it should be as transperant to the programmer as possible. when i write something like: ones = 1 : ones
i don't think of "printing infinately many ones in memory" and i don't see why i should start thinking of it that way just because i want to make the object persistant. after all, one can think of the disk as a verys low memory.
Ok, it seems that you're really after persistence as opposed to just serialisation, which is what the Binary library provides. I'm not aware of any working implementations of this kind of persistence for current compilers, but it wouldn't be too much work to implement in GHC, as long as you don't mind the persistent data being only readable by particular binary that generated it, and refrain from any dynamic linking of Haskell code. Cheers, Simon