I'm currently playing with Reflex, a wonderful functional reactive programming library that lets you compile the same code into into webapps with GHCJS (a JavaScript backend for GHC) or into standalone desktop apps (using WebKitGTK).

It's wonderfully expressive and doesn't feel like you're painfully imitating C++ in Haskell. On the contrary, it's very idiomatic.

https://github.com/reflex-frp/reflex

However, FRP is ... unusual, and takes a bit of time to get the hang of.

Here's a stripped-down todo app "tutorial" in Reflex:

https://gist.github.com/mrkgnao/1a5c06cc1e188f2238c8c11cb74e...

And this is a full-featured TodoMVC in Reflex:

https://github.com/reflex-frp/reflex-todomvc

--

FLTK is a GUI toolkit that has Haskell bindings. It's a very C++-like API, but the library is in heavy development.

https://github.com/deech/fltkhs

The developer is also quite friendly, and I believe there are good docs. Here are a few demos:

https://github.com/deech/fltkhs-demos

Also, GHC does have a C backend, afaik, although it's deprecated nowadays and only available if you build it yourself in "unregisterised mode", which people do when porting GHC to a new architecture.