Double colons

[sniffnoy]

Something I meant to post but forgot (quotes naturally inexact). So Peter was explaining products and coproducts to Youlian - I was around, doing something else. Naturally two example categories that he used were the category of topological spaces and the category of R-modules. And so after a bunch of explaining...

Youlian: Huh. I always thought of it as box toplogy:direct product :: product topology:direct sum.
Me, butting in: ...but a better analogy is product topology:direct product :: disjoint union:direct sum.

I just posted this because I thought the two analogies put side by side made a nice-sounding parallelism...

-Harry