On Fri, 20 Jul 2012, Brent Yorgey wrote:
Use of GHC.Exts ---------------
At the request of a user, the 0.1.4.3 release switched from defining its own version of the standard 'build' function, to importing it from GHC.Exts. This allows GHC to do more optimization, resulting in reported speedups to uses of splitEvery, splitPlaces, and splitPlacesBlanks. However, this makes the library GHC-specific. If any reviewers think this is an issue I would be willing to go back to defining build by hand, or use CPP macros to select between build implementations based on the compiler.
You could provide two private modules with the same name in different directories, one that re-exports 'build' from GHC.Exts and one with a custom definition of 'build' for non-GHC compilers. Then set 'Hs-Source-Dirs' in Cabal according to the impl(ghc). No CPP needed, only Cabal. One could even think of a separate package for this purpose. The only type extension you use, is GADTs, right? It looks like you use it for an Eq constraint in Delimiter/DelimSublist. That is, you actually need only ExistentialQuantification. Is it necessary?