Hi, could anyone help me with some answers and/or some recommendations about what to read (hopefully at a higher level than the source code :-) ) to get the answers to the following questions (I've read the current ffi & hdirect documentation & examples and ffi-list archives but couldn't find anything to answer these questions): (1) The hdirect documentation appears to say that anything other than a primitive type can only be returned as an abstract datatype. If this is correct, is there any common way people have come up with to tackle returns of datatypes (primarily lists) to some sort of datastructure that can be examined directly in C (well, C++)? (2) Regarding calling C++ from Haskell, is it correct that all functions being called have to be `extern C' because of C++-name-mangling? Other than being inelegant, is there anything to prevent me trying to hack on a stage in the foreign code interface stuff that compares the output of `nm' and `nm --demangle' to do automatic conversion into mangled-names when there is no overloading going on. (I ask this because it would minimise the changes needed to the C++ source code to call C++ functions.) To explain these questions, I'm interested in being able to use Haskell more aggressively in developing prototype code (for visual analysis). At present I write small independent Haskell scripts that test an algorithm using synthetic test data; I'm looking at being able to call Haskell prototype code directly from the main C++ application. (This would have the advantage of being able to run the prototype code on real data generated by the preceding C++ code.) Thus, unlike most of the FFI stuff I see talked about in the documentation (which describes situations where one of the sets of source code is essentially stable), the source code in _both_ languages is extremely changeable. My interest in `low programmer-overhead interfacing' is that my job is currently `image processing' and nothing else; consequently if it takes more time working with the interfacing tools than is saved by easier prototyping in haskell I can't justify doing it. Many thanks of any assistance anyone is able to provide, ___cheers,_dave________________________________________________________ www.cs.bris.ac.uk/~tweed/pi.htm |tweed's law: however many computers email: tweed@cs.bris.ac.uk | you have, half your time is spent work tel: (0117) 954-5250 | waiting for compilations to finish.