[Haskell-cafe] Data.Set.member vs Data.List.elem

Hi, Is there a good reason that Data.Set uses the name "member" while Data.List (or the Prelude) uses the name "elem", for what to me seem identical concepts. I realise that in Set's the traditional test is for "membership", but it seems awfully arbitrary that one jumped one way and one jumped the other. I've just written an entire module's worth of Haskell with Set.elem, as that "felt" right, now I'm going back and fixing it. Thanks Neil