2. if your function returns Ptr a - then hold in haskell types this Ptr a. no need to convert it back and forth to ForeignPtr Yes, I thought of doing this, but then thought it was better to use a so-called "managed" foreign pointer via newForeignPtr. I thought this was the best way to have a foreign pointer that the Haskell garbage collector would eat up when it was no longer in use. I could be wrong. I convert from a ForeignPtr to a Ptr, because the FFI code wasn't compiling at all (nevermind the missing C/C++ reference
Bulat, Some very good suggestions. I will try to appease Ceiling Cat and reduce my (perhaps gratuitous) use of unsafePerformIO. I'm going to have to use it somewhere, since I want referentially transparent code (and I try to avoid the IO monad when possible, anyway). problem), as apparently a ForeignPtr isn't the sort of thing that an imported foreign function can take as an argument (or so said GHC). I just assumed that the back-and-forth between Ptr and ForeignPtr would be compiled away by GHC. I could be wrong, though. If performance starts to suffer, I'll manage the Ptr memory in my code directly.
4. i don't looked in your code but if C functions defines *modifiable* datastructure - you should use it at Haskell side via imperatiove functions, i.e. those with return type IO a. using unsafePerformIO in this case will lead to Haskell compiler will consider this datatype as permanent and reorder operations on the will
Good point. I would do this if I planned to train or update the language model from within Haskell, but, as it stands, I just want to train it once (at the command line, using the built-in mechanisms of SRILM) and then read in the ARPA-formatted language model file for use in Haskell.
3. why c_dlm is FunPtr in your definition? it should be
foreign import ccall "srilm.h deleteLM" c_dlm :: Ptr Ngram -> IO () No reason. Just because I don't know what I'm doing yet. Thanks for the correction.
Thanks for the help, Bulat. Much appreciated. Best, Dennis -- View this message in context: http://old.nabble.com/FFI%2C-C-C%2B%2B-and-undefined-references-tp27139612p2... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.