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feat(analysis/normed_space/lattice_ordered_group): Lattice ordered group lemmas #9548

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@mans0954 mans0954 commented Oct 4, 2021

Adds some useful lattice ordered group lemmas, needed by #10322.


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mans0954 and others added 7 commits October 5, 2021 18:30
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
@mans0954 mans0954 added the awaiting-review The author would like community review of the PR label Oct 6, 2021
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ocfnash commented Nov 22, 2021

Thank you for this PR @mans0954 and thank you for your patience with this PR.

I'm sorry that this proposal has been open for so long without resolution so I've just taken a careful look to see what we can do. It looks to me like there are four things happening here:

  1. Introducing classes has_pos_part, has_neg_part and associating these with the postfix notation , instead of mpos and mneg.
  2. Changing many comments in src/algebra/lattice_ordered_group.lean
  3. Adding some new lemmas e.g., abs_abs_div_abs_le, two_inf_sub_two_inf_le etc.
  4. Making changes to very fundamental stuff like introducing a multiplicative version of sub_add_cancel except it has to be called div_mul_cancel' rather than div_mul_cancel because the latter is already taken for a group_with_zero rather than a plain group.

Do you think you would be able to split it up, into several PRs, perhaps (but not necessarily) along the lines above so that it is easier to focus on each of the various changes?

Though the various pieces are related, each of them is likely to need discussion in its own right.

@ocfnash ocfnash added awaiting-author A reviewer has asked the author a question or requested changes and removed awaiting-review The author would like community review of the PR labels Nov 22, 2021
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Do you think you would be able to split it up, into several PRs, perhaps (but not necessarily) along the lines above so that it is easier to focus on each of the various changes?

I could do that it it would help? 1) and 2) were the outcome of previous review of this PR #9548 (review) #9548 (review) and 4) is motivated by feedback on a previous PR #8663 (review) and #8673 (comment) .

The impact of changes 1) and 2) is limited to code I wrote in my recent PRs #8673, #9172, #9274, which, together with this PR are building towards #10322.

@github-actions github-actions bot added the blocked-by-other-PR This PR depends on another PR which is still in the queue. A bot manages this label via PR comment. label Nov 22, 2021
bors bot pushed a commit that referenced this pull request Nov 23, 2021
…multaplicative form (#10419)

Currently mathlib has a rich set of lemmas connecting the addition, subtraction and negation additive group operations, but a far thinner collection of results for multiplication, division and inverse multiplicative group operations, despite the fact that the former can be generated easily from the latter via `to_additive`.

In  #9548 I require multiplicative forms of the existing `sub_add_cancel` and `neg_sub` lemmas. This PR refactors them as the equivalent multiplicative results and then recovers `sub_add_cancel` and `neg_sub` via `to_additive`. There is a complication in that unfortunately `group_with_zero` already has lemmas named `inv_div` and `div_mul_cancel`. I have worked around this by naming the lemmas in this PR `inv_div'` and `div_mul_cancel'` and then manually overriding the names generated by `to_additive`. Other suggestions as to how to approach this welcome.
@github-actions github-actions bot added merge-conflict Please `git merge origin/master` then a bot will remove this label. and removed blocked-by-other-PR This PR depends on another PR which is still in the queue. A bot manages this label via PR comment. labels Nov 24, 2021
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🎉 Great news! Looks like all the dependencies have been resolved:

💡 To add or remove a dependency please update this issue/PR description.

Brought to you by Dependent Issues (:robot: ). Happy coding!

@github-actions github-actions bot removed the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Nov 24, 2021
ericrbg pushed a commit that referenced this pull request Nov 24, 2021
…multaplicative form (#10419)

Currently mathlib has a rich set of lemmas connecting the addition, subtraction and negation additive group operations, but a far thinner collection of results for multiplication, division and inverse multiplicative group operations, despite the fact that the former can be generated easily from the latter via `to_additive`.

In  #9548 I require multiplicative forms of the existing `sub_add_cancel` and `neg_sub` lemmas. This PR refactors them as the equivalent multiplicative results and then recovers `sub_add_cancel` and `neg_sub` via `to_additive`. There is a complication in that unfortunately `group_with_zero` already has lemmas named `inv_div` and `div_mul_cancel`. I have worked around this by naming the lemmas in this PR `inv_div'` and `div_mul_cancel'` and then manually overriding the names generated by `to_additive`. Other suggestions as to how to approach this welcome.
@github-actions github-actions bot added the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Dec 3, 2021
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mans0954 commented Dec 4, 2021

I think everything of use in this PR has now been merged via other smaller PRs, so closing.

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5 participants