making language tools in windows is actually quite challenging due to the poor quality of tools. its the only thing i've ever struggled with in that area. using haskell and llvm makes it a little easier than using C and llvm but not much...
it would be nice to have a windows friendly set of instructions - setting up GHC, happy, alex etc. isn't hard, but LLVM is a pain for windows.
it would be nice if it was in C rather than Haskell too. imo its highly likely nobody wants to touch Haskell if they have a choice. then the many C tools one might want to use like flex, bison - even win-flex and win-bison are a bit rubbish and difficult to configure for use in windows...
still a very useful article - its great to see an example worked through like this, its one of the best forms of documentation imo and not enough of that around in this area...