Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[Merged by Bors] - feat(category_theory): preadditive binary biproducts #2747

Closed
wants to merge 5 commits into from

Conversation

TwoFX
Copy link
Member

@TwoFX TwoFX commented May 19, 2020

This PR introduces "preadditive binary biproducts", which correspond to the second definition of biproducts given in #2177.

  • Preadditive binary biproducts are binary biproducts.
  • In a preadditive category, a binary product is a preadditive binary biproduct.
  • This directly implies that AddCommGroup has preadditive binary biproducts. The existence of binary coproducts in AddCommGroup is then a consequence of abstract nonsense.

@TwoFX TwoFX added the awaiting-review The author would like community review of the PR label May 19, 2020
@TwoFX
Copy link
Member Author

TwoFX commented May 19, 2020

Originally, I for some reason believed that in a preadditve category, every binary biproduct is automatically a preadditive binary biproduct. This is of course not true, which makes this PR a bit less nice than I had originally hoped, but I hope it's fine.

This PR introduces two erws into Preadditive.lean. [Originally I wanted to write here that they should be relatively easy to remove, but I just tried and it doesn't seem to be as trivial as I had anticipated]. If there is strong interest in getting rid of them, I can look into it.

Copy link
Member

@jcommelin jcommelin left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

LGTM

src/category_theory/limits/shapes/biproducts.lean Outdated Show resolved Hide resolved
src/algebra/category/Group/biproducts.lean Show resolved Hide resolved
@jcommelin
Copy link
Member

Thanks 🎉

bors merge

@github-actions github-actions bot added ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.) and removed awaiting-review The author would like community review of the PR labels May 22, 2020
bors bot pushed a commit that referenced this pull request May 22, 2020
This PR introduces "preadditive binary biproducts", which correspond to the second definition of biproducts given in #2177.

* Preadditive binary biproducts are binary biproducts.
* In a preadditive category, a binary product is a preadditive binary biproduct.
* This directly implies that `AddCommGroup` has preadditive binary biproducts. The existence of binary coproducts in `AddCommGroup` is then a consequence of abstract nonsense.
@bors
Copy link

bors bot commented May 22, 2020

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(category_theory): preadditive binary biproducts [Merged by Bors] - feat(category_theory): preadditive binary biproducts May 22, 2020
@bors bors bot closed this May 22, 2020
@bors bors bot deleted the preadd branch May 22, 2020 07:28
cipher1024 pushed a commit to cipher1024/mathlib that referenced this pull request Mar 15, 2022
…unity#2747)

This PR introduces "preadditive binary biproducts", which correspond to the second definition of biproducts given in leanprover-community#2177.

* Preadditive binary biproducts are binary biproducts.
* In a preadditive category, a binary product is a preadditive binary biproduct.
* This directly implies that `AddCommGroup` has preadditive binary biproducts. The existence of binary coproducts in `AddCommGroup` is then a consequence of abstract nonsense.
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.)
Projects
Homological algebra
  
Awaiting triage
Development

Successfully merging this pull request may close these issues.

None yet

2 participants