GHCi does this somehow, so it's definitely possible; Simon M will know. | -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users- | bounces@haskell.org] On Behalf Of wren ng thornton | Sent: 06 December 2011 17:49 | To: GHC-users List | Subject: Revert a CAF? | | So, I have an optimization/internals question. Does the GHC API have any | hooks for being able to revert a CAF to the original expression, thus | discarding the previously computed result? | | The reason I'm wanting this is that I have a particular CAF which is an | infinite list. Unfolding that list takes a fair deal of work, so we want | to share it whenever possible; however it doesn't take an overwhelming | amount of work, so if we know we've evaluated more of the list than | necessary (for a long while), it'd be nice to be able to revert the | evaluation in order to save on memory overhead (e.g., by calling relax | :: IO()). | | I could hack something together based on unsafePerformIO and top-level | IORefs, and it's clear that this is in fact a safe thing to do, but I'm | worried about the semantic issues inherent in unsafePerformIOed | top-level IORefs (e.g., the fact that their scope isn't particularly | well defined: is it per library instance? per runtime?...). | Unfortunately, for what I'm doing, it isn't really feasible to just | leave the IO type in there nor to pass around the infinite list so we | can use scoping rules to decide when to free it. | | (Feel free to offer alternative suggestions to handling this situation too.) | | -- | Live well, | ~wren | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users