On 20 Sep 2009, at 06:21 , Bruce Leban wrote: I don't quite understand what you are trying to solve. Here's a related
problem: One of the issues with duck typing is that something might look sort of like a duck but isn't really and it would be nice to make it easy to avoid using an object in a "half-baked" manner:
def playWithDuck(d): d.walk() d.quack()
if someone calls playWithDuck(dog) then the dog's going to get walked before trying to make the dog quack fails.
Note that with a structural type system (that of OCaml's objects for instance) this will work, the `playWithDuck` function will be inferred to take any subtype of < walk : unit; duck : unit > (or something like that) (basically, any object with a `walk` and a `quack` method (both returning nothing) will work).