using IORefs, one can construct linked lists in Haskell that resemble one's used in imperative C programming.

eg, the following toy code creates a chain of 1000 linked records.

import IOExts

data Record= RecordNil | Record String Int Chain type Chain = IORef Record

main=makeChain [1..1000]

makeChain::[Int]->IO Chain makeChain []=newIORef RecordNil makeChain (a:as)=makeChain as>>= \chain-> newIORef (Record "data" a chain)

such structures will be garbage-collected "automatically", right?

Yes.

in general terms, please comment on how well GHC supports code that uses such structures.

It should work fine.

now, to turn makeChain into a "lazy producer" requires adding an IO to the type of Chain, yielding

type Chain=IO (IORef Record)

please comment on how well GHC would tend to support such a type.

I'm not sure exactly what you mean by "support" in this context, but I'm not aware of any known bugs that would impact your use of the above type. Cheers, Simon