Hi all, I hope everyone had a nice holiday season. I am picking up a project that I started a few years ago, but for various reasons stopped working on. It was the Libraries for Digital Signal Processing listed in the Numerical Algorithms and Mathematics section on the haskell.org website. I am going to revisit those libraries and expand the scope a little bit to include spectral estimation and some matrix math routines. Anyway, since I haven't done any Haskell in about three years, I am a bit rusty. :) I have one question right now, and would like some advice on another matter. I am sure I will have other questions until the proper section of my brain wakes up. First, I cannot get a function to type. The basic definition is: rxx x k | k >= 0 = sum [ (conjugate (x!k)) * x!(n+k) | k <- [0..(n-1-k)] ] / n | k < 0 = conjugate (rxx x (-k)) where n = snd (bounds x) + 1 This function performs autocorrelation for a complex array, and returns a complex value. The array indexes are integral in the general sense, but could be safely Int. I have tried various combinations of explicit types and numeric type coersion functions without any success. Any help would be appreciated. The second question has to do with the numeric class system. In signal processing and spectral estimation, there are a lot of algorithms that can operate on real and complex data. In most cases, the only difference is the complex versions have conjugates in various places. In the function above, the equivalent real valued version is the same if you either get rid of the conjugate applications, or assume that the conjugate function for real numbers is the identity function. What is the best way to handle this? I don't want to have separate functions for real and complex data, but I'm not sure of the proper way to add conjugate=I to to the class system for non-complex numbers. Thanks. PS, if anyone wants a preview of my LU decomposition module (ie, it could stand a bit more testing), please let me know. -- Matthew Donadio (m.p.donadio@ieee.org)