Covariance

[Dave]

Hello all,

I had thought that both return types and parameter types of virutal
functions could be covariant. However, looking in the Standard (electronic
search), I find reference to only return types being allowed to be covariant
(10.3/5). Also, I thought I remembered the notion of contravariance
existing as well, but I don't find that either. Can anybody point me to the
relevant sections that address these issues?

Thanks!
Dave

 

[Phlip]

I had thought that both return types and parameter types of virutal
functions could be covariant. However, looking in the Standard (electronic
search), I find reference to only return types being allowed to be covariant
(10.3/5). Also, I thought I remembered the notion of contravariance
existing as well, but I don't find that either. Can anybody point me to the
relevant sections that address these issues?

A method's "signature" everything from its name to the right.

Signatures bind at compile time, before virtual method lookup at runtime.

So only virtual method lookup can covariate.