abuseofnotation / category-theory-illustrated

A book about category theory
https://abuseofnotation.github.io/category-theory-illustrated/
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Singlton Example #26

Closed phikal closed 1 year ago

phikal commented 2 years ago

In the "Singleton Set" section it says:

The set of books written by the American writer Harper Lee and published during her lifetime is a singleton set - she has published just one novel.

Which isn't quite true, since 2015 she published "Go Set a Watchman".

I know this is being pedantic and not the point of the explanation, but I guess it could confuse someone who knows a lot more about American literature than set theory.

abuseofnotation commented 2 years ago

Haha, well to my defense this was written before 2015.

What are some examples of writers with one published book?

phikal commented 2 years ago

boris @.***> writes:

Haha, well to my defense this was written before 2015.

What are some examples of writers with one published book?

Here is a list I found[0]:

But maybe there are other singleton examples that are just as intuitive? A shed has a single room, so the set of rooms is a singleton? A unicycle has a single wheel, so the set of wheels is a singleton? Every country has a single capital, so the set of capitals are always a singleton by necessity?

[0] https://www.goodreads.com/list/show/5477.Authors_With_Only_One_Novel

AlexPl292 commented 1 year ago

On a sad note, I also would like to add that "The set of queens of England" is now not a "singleton set", but an "empty set".

abuseofnotation commented 1 year ago

I rewrote the example about the queens of England and decided to remove the second example.

The example with the king/queen is good because the king/queen is one by definition (the one with the capital is good too, but it is conceptually very similar to the one with the one about the kings)

Thanks @phikal, for the suggestions.