Duadic Codes over F 2 + u F 2

Duadic codes over F2+uF2 are introduced as abelian codes by their zeros. This is the function field analogue of duadic codes over Z4 introduced recently by Langevin and Sol é. They produce binary self-dual codes via a suitable Gray map. Their binary images are themselves abelian, thus generalizing a result of van Lint for cyclic binary codes of even length. We classify them in modest lengths and exhibit interesting non-cyclic examples.