On Wed, Aug 10, 2011 at 10:29 AM, Robert Fischer
<[email protected]> wrote:

> Can you define "contra-" and "co-" variance for me in the context of
> structural (not nominal) typing?

Whether a type system is structurally or nominally typed is orthogonal
to whether it has subtyping.  Algol 68 records, which are structural
types, have no subtypes; but Go interface types, which are also
structural types, do have subtypes.  The co- and contravariance
problem arises wherever there are static types with subtyping.

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