Hey, folks. I've got a problem which I've thought about for days. I need to write a program that mixes C and haskell code. And the C code controls the procedure. In C code, I want to save a complex data strcuture defined in haskell and pass it back to a haskell function at certain time. Like the following: in haskell: data A = A {...} -- very very complex data structure initA :: A initA = A {...} func :: A -> A func a = ... -- return a new 'A' in C: main { a = initA ... take some actions a = func a; ... take some other actions a = func a; ... ... } Different from most cross-language programs, this C program doesn't alter the data in haskell, just saves it and passes it on. So I'm wondering if there's some convienent way other than marshalling the data in haskell? BTW, mashalling data requires all work done in IO monad, which will change the program stucture. So I really don't want to mashal it. Thank you!