Dear Haskellers, I have a question about the FFI and interfacing to C++ via C. I want to use funcionality that I have implemented a while ago using C++ classes, and I also see this as an exercise on how to create wrappers using the Haskell FFI. The class I want to wrap first is a matrix class. Here is the thing: In order to create a matrix object, I create a C function that calls the C++ new operator, creating a matrix object, and returning it as a void pointer. Deletion is handled analogously. Then in Haskell, I import the two functions, and I have a matrix type like this: newtype Matrix = Matrix (Ptr Matrix) From this I create a ForeignPtr with newForeignPtr, giving the deletion function (which calls the C++ destructor for a matrix) as finalizer. Testing this showed me that it does work. /But/: So far everything is happening in the IO monad. However, I want to be able to work with matrices outside IO. Now, of course memory allocation can fail, and I don't want to use something like unsafePerformIO when there can actually be a failure when calling the constructor for a matrix. Is there a recommended way to do this? Also, is there a way to get memory from the Haskell runtime system in a safer way and construct the object in that memory? I hope I could make myself clear enough, as usual thanks for any hints!! Christian