The attached represents success (I think/hope<g>) with getting GSL to fit a Gaussian plus a line to some data. I hope to use this to measure widths of peaks in FFTs of specific signals. The bad news is that I can't get Alien callbacks to work. Actually, the callbacks seem to work just fine, but I get "invalid number of arguments" and other errors as the function that calls the callbacks is either finishing up, close to that, or returns. FWIW, that call is made via FFI. The nature of the problem is not clear, and I lack the vm skill to reasonably think I could debug it. Using C functions to define the residuals and jacobians works perfectly, so I am on the (presumptuous) edge of thinking that my code is not the problem. Any ideas? Bill
