4 msΒ·
> A set π is jaberwocky when for every π₯βπ there exists a bryllyg πβπ and an uffish πΎβX such that π₯βπ and πβπΎ. Anyone know how this relates to Lewis
by jakear 6y ago
> A set π is jaberwocky when for every π₯βπ there exists a bryllyg πβπ and an uffish πΎβX such that π₯βπ and πβπΎ.
Anyone know how this relates to Lewis Carrol?
- creata 6y agoJabberwocky is a poem by Lewis Carroll. https://en.wikipedia.org/wiki/Jabberwocky https://en.wikipedia.org/wiki/Jabberwocky
- schoen 6y agoAnd the idea in the context of the original post is that this is supposed to be a parody of a formal math definition in a paper or textbook (using Jabberwocky vocabulary instead of real math vocabulary).
- newen 6y agoNot that it makes sense anyway. Somehow πβπ and πβπ.
- leanuser83 6y agoThat is exactly the point being made. That you can spot right away that something "doesn't make sense".
- skissane 6y agoNo, the point was that πβπ is a typo and πβπ is what was intended. Type theory will reject the mistake but set theory will accept it. This is then presented as a reason why mathematicians should prefer type-theory-based proof assistants to set-theory-based ones, since the former will catch these kinds of mistakes while the later won't.
- bobbylarrybobby 6y agoThatβs possible. For instance, X = {{}} and U = {}. Or in general, if X_0 = {} and X_{i+1} = {X_0, ..., X_i}, then X_i is both an element and a subset of X_j whenever i < j.
- contravariant 6y agoThat happens all the time with ordinals.
- pfortuny 6y agoIt is just a way to hide the definition of local compactness of a topological space with a mistake (should be U included in K).