What is your recommendation for type-level integers? I'd like to use it to improve the unittyped, https://bitbucket.org/xnyhps/haskell-unittyped/ the library for physical dimension. Therefore, I need negative numbers, additions, but multiplications are not necessary. I've been looking forward for the type-nats extension of GHC, but I haven't been able to compile the type-nats branch. Just learned that it still takes a few month to merge the branch into the main. http://hackage.haskell.org/trac/ghc/wiki/Status/May13 Thijs, the original author of unittyped, has commited a branch that uses type-nats, but I can't try that out for the same reason. Best, -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html