On Mon, Mar 23, 2020 at 06:03:06PM -0700, Andrew Barnert wrote:
The existing methods are named issubset and issuperset (and isdisjoint, which doesn’t have an operator near-equivalent). Given that, would you still want equals instead of isequal or something?
Oops! I mean, aha, you passed my test to see if you were paying attention, well done!
I would be satisfied by "isequal", if the method were needed.
So, I’d rather have an uglier, more explicit, and more obviously specific-to-set name like iscoextensive. Sure, not everyone will know what “coextensive” means
That's an unnecessary use of jargon that doesn't add clarity or precision and can only add confusion. Outside of the tiny niche of people trying to prove the foundations of mathematics in first-order logic and set theory, when mathematicians want to say two sets are equal, they say they are equal, they don't use the term “coextensive”.
See, for example, Mathworld, which uses "=" in the usual way:
and doesn't even have a definition for “coextensive”:
The foundations of mathematics is one of those things which are extremely over-represented on the Internet compared to the experience of real-life mathematicians. Gödel's Theorems are another one. My cousin is a professor of mathematics at Rutgers and when I asked her about Gödel her response was "Who?".
Mathematics is huge. Working on the foundations is a tiny niche, in the same way that the set of people working with electronics is huge while the set of people working on the foundations of how electrons travel through copper wires at a quantum mechanical level is tiny.