Tony Morris

@puffnfresh @dibblego @jedws @tpolecat @nuttycom Then what *do* you use? Define it for me please.

@djspiewak @dibblego @jedws @tpolecat @nuttycom I talk about equivalence with laws, absolutely not structural equality.

@puffnfresh @dibblego @jedws @tpolecat @nuttycom What is equivalence?

@djspiewak @dibblego @jedws @tpolecat @nuttycom http://ncatlab.org/nlab/show/principle+of+equivalence …

@puffnfresh @djspiewak @dibblego @tpolecat @nuttycom good link, failure of equivalence preservation is the fundamental issue here

@puffnfresh @djspiewak @dibblego @tpolecat @nuttycom I like the idea that breaking equivalence invariance is evil – Arch Dr Functor[Set]

@jedws @puffnfresh @dibblego @tpolecat @nuttycom Exactly. :-) I think Functor[Set] may be the archetypical symptom of this. Not the only one

@djspiewak @puffnfresh @dibblego @tpolecat @nuttycom Functor type (not notion) is forall a -> b, but Set is constrained to things with Eq