I was working on a re-implementation of the Integer type in pure Haskell earlier this summer, represented by [Int], thinking it might be useful as a less-broken alternative to GMP than using plain Int for Integer. The code turned out around 500-1000 lines. It got pretty much working (in yhc, ghc, and hugs; according to QuickCheck comparing the results with native Integer anyway), though the code's still somewhat messy ...and large Integer division seems to be sometimes slower than expected (maybe a strictness issue, haven't looked into it) ...although, all functions are fast for small values that fit in one Int. Is anyone interested in more details or work on this? (P.S. I wonder if I should ask any other mailing list than yhc's?) Isaac