The current documentation for Data.Array.IArray.amap says what it does, but doesn't say anything about how it should (and shouldn't!) be used. Specifically, it does not implement amap/amap or amap/coerce rules, and it probably cannot do so safely if the IArray instance does not satisfy the appropriate lens-like laws. Thus the most appropriate way to use this function is probably to implement the Functor instance for an IArray type, using type-specific RULES. It's probably *not* such a hot idea to use this amap directly. I don't know if all that should be crammed, with explanation, into the Haddocks or if there's a better way to handle it. David