I've changed GHC's implementation so that it now displays just the filename from the Handle (this is the the only immutable part of the Handle).
I share Alastair's concern about the possibility that a handle may not always contain a filename. I think it would be cleaner to assume that the only immutable part of a handle is its identity. And it is important that the identity be shown (that is, as by `show`). I think we should we specify that `show`ing a `Handle` gives: "Handle " ++ handleId or "(Handle " ++ handleId ++ ")" depending in the usual way on the current precedence, and where `handleId` is implementation-defined but required to identify the handle uniquely within the current process.
This raises another question though: should there be an IO
operation for displaying the more interesting parts of a Handle? I propose:
System.IO.hShow :: Handle -> IO String
Sounds good.
I agree. I am content to leave the form of output implementation-defined. -- Dean