Source repository is on github.
If you "cabal unpack language-objc; cd language-objc-0.4.2.0/examples/", there are a number of examples that can get you started. For the truly impatient:
A few things to note:
import Language.ObjC import qualified Data.ByteString.Char8 as B -- parsing bytestrings objcTranslUnit = B.pack "int a=0;" errOrAST = parseC objcTranslUnit nopos -- parsing from a file fileAST sourceFile = do result <- parseCFile (newGCC "gcc") Nothing  sourceFile return $ either (error . show) id result
- Input files must be preprocessed. 'parseCFile' will do this for you. Non-preprocessed source can only be parsed in very limited situations (did you know that 'id' is a typedef? And 'id' is also commonly used as an identifier to methods/functions, even in system libraries, so it can't be a keyword?).
- The objective-C extensions have only been lightly tested, but I think most of the core functionality works. I am unaware of a full specification for the language, which makes it difficult to say if it's complete.
- Most of the code in Language.ObjC.Analysis is not yet compatible with Objective-C extensions.
- One difference from language-c is that certain GNU attributes can no longer be parsed due to grammar ambiguities.
- Attempting to compile at -O2 requires a lot of memory due to the giant Happy parser that's produced.
I am most grateful to Benedikt Huber, Manuel Chakravarty, Duncan Coutts, Bertram Felgenhauer, and all contributors to language-c, as they're responsible for most of the code. Bugs are mine. Comments and patches welcome.