4 ms·

Nice! Note that this page has no category theory yet since it explains sets, so if you already know sets, set product, etc and want to learn about category the

by xjm 3y ago

Nice! Note that this page has no category theory yet since it explains sets, so if you already know sets, set product, etc and want to learn about category theory, my advice is to go directly to the next chapter, more specifically to this section: https://abuseofnotation.github.io/category-theory-illustrated/02_category/#defining-products-in-terms-of-functions https://abuseofnotation.github.io/category-theory-illustrate... which uses set theory terms to define the category theory way of defining products (the corresponding "universal property").

munchler 3y ago
I really like this approach, but it contains some confusing mistakes. For example, unless I'm very much mistaken, the illustration of the initial object is backwards: https://abuseofnotation.github.io/category-theory-illustrated/02_category/initial_object.svg https://abuseofnotation.github.io/category-theory-illustrate...
- JadeNB 3y ago
  > For example, unless I'm very much mistaken, the illustration of the initial object is backwards: https://abuseofnotation.github.io/category-theory-illustrated/02_category/initial_object.svg https://abuseofnotation.github.io/category-theory-illustrate... You are right. (Curiously, the picture of the terminal object is correct, so they didn't just switch them!)
- slacka 3y ago
  The author said he is just starting on the book, so he's not claiming it's perfect. And the beauty of github, open source is you can fix them with a pull request. For example, the svg is here: https://github.com/abuseofnotation/category-theory-illustrated/blob/master/_chapters/02_category/initial_object.svg https://github.com/abuseofnotation/category-theory-illustrat...
- haskman 3y ago
  Looks fine to me. What's wrong with it?
  - boris_m 3y ago
    Author here. It was backwards, I fixed it when I saw the comment. Feel free to report any other mistakes you see on https://github.com/abuseofnotation/category-theory-illustrated https://github.com/abuseofnotation/category-theory-illustrat... or email.
    - haskman 3y ago
      Seems you might have fixed it before I saw it! Thanks!

by xjm 3y ago

munchler 3y ago

I really like this approach, but it contains some confusing mistakes. For example, unless I'm very much mistaken, the illustration of the initial object is backwards: https://abuseofnotation.github.io/category-theory-illustrated/02_category/initial_object.svg https://abuseofnotation.github.io/category-theory-illustrate...

JadeNB 3y ago
> For example, unless I'm very much mistaken, the illustration of the initial object is backwards: https://abuseofnotation.github.io/category-theory-illustrated/02_category/initial_object.svg https://abuseofnotation.github.io/category-theory-illustrate... You are right. (Curiously, the picture of the terminal object is correct, so they didn't just switch them!)
slacka 3y ago
The author said he is just starting on the book, so he's not claiming it's perfect. And the beauty of github, open source is you can fix them with a pull request. For example, the svg is here: https://github.com/abuseofnotation/category-theory-illustrated/blob/master/_chapters/02_category/initial_object.svg https://github.com/abuseofnotation/category-theory-illustrat...
haskman 3y ago
Looks fine to me. What's wrong with it?
- boris_m 3y ago
  Author here. It was backwards, I fixed it when I saw the comment. Feel free to report any other mistakes you see on https://github.com/abuseofnotation/category-theory-illustrated https://github.com/abuseofnotation/category-theory-illustrat... or email.
  - haskman 3y ago
    Seems you might have fixed it before I saw it! Thanks!