I’ve started my journey with Haskell not so long ago, but because that was my third approach, I didn’t want to do only small projects, as it would surely not motivate me enough. I was looking for some kind of project that will not be too complicated and I will be able to make open source. That’s how the idea for a hLibsass and a hSass arose. My pull request to include them in Stackage has just been accepted, so I think it is high time to write about them. ;)
Basically, these libraries are wrappers over LibSass, a C++ implementation of a Sass compiler. The former is very low-level, as it consists of FFI bindings only and has just the same feature set as a C interface of LibSass.
hSass is a more interesting one, as it has more code and let me really appreciate Haskell. It is just a couple of types and functions, but I think it covers most of the features of LibSass. You can compile strings, files, use Haskell functions in Sass code and examine all the information LibSass provides.
Quick example:
import Control.Monad ((>=>))
import System.Environment (getProgName, getArgs)
import Text.Sass
main :: IO ()
main = do
progName <- getProgName
args <- getArgs
case args of
(f:_) -> compile f
_ -> putStrLn $ "Usage: " ++ progName ++ " FILE"
compile :: FilePath -> IO ()
compile file = do
result <- compileFile file def
either (errorMessage >=> putStrLn) putStrLn result
And we have a simple, standalone Sass compiler.
If you want to play with these libraries, go ahead and cabal install or stack install them (next Stackage nightly build should have them). If you want to use them with GHCi you must compile hLibsass with a shared version of LibSass (there is some sort of a bug in GHC’s runtime system that prevents hLibsass to correctly load, but I have not been able to dig into it deep enough yet) - just use the flag sharedlibsass (as described in a README).