I'm having some problems with Numeric.AD (translation, things are not working for reason that I don't understand). Note I don't have much experience with this package, so these are newbie questions, thus appropriate answers may involve pointing me to a document somewhere out there on the net. Anyway, here is my problem: I have a function (call it f x theta) which I have defined purely in terms of basic arithmetic functions (+/-/(/)/*/**) glued together using standard applicative functor operations has type f :: m1 (m2 Double) -> m3 Double -> Double f x theta = ... m1 m2 and m3 are all Traversable. f is defined purely in terms of basic arithmetic operations, (+/-/(/)/*/**) glued together using standard applicative functor operations, and m1 m2 and m3 are all pretty trivial record types (no recursion, even). I would like to write df x theta = grad (f x) theta But it refuses to type, even though (admittedly quite a lot) simpler versions do. So what am I missing? Does AD not go through Applicative? That seems unlikely to me. Any advice / suggestions, etc. gratefully received. Sean Matthews -- Sean Matthews seanmatthews1@gmail.com / +49 1515 800 1901