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feat(algebra/module): scalar multiplication on the right is injective #7548

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This is a split-off dependency from #7496.


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@Vierkantor Vierkantor added the awaiting-review The author would like community review of the PR label May 8, 2021
@@ -461,9 +461,17 @@ end add_comm_group

section module

variables {R} [ring R] [add_comm_group M] [module R M] [no_zero_smul_divisors R M]

lemma smul_right_injective {x : M} (hx : x ≠ 0) :
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I think R should probably be explicit here. Is M explicit for smul_left_injective?

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Both R and M are implicit in smul_left_injective. I guess it depends whether we want to treat injective like iff, that arguments inferable from applying injective can be left implicit.

I could also wait for #7496 to be merged, then open a PR for making the parameters for smul_left_injective and for smul_right_injective explicit.

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I must have been imagining that smul_left_injective even exists; I found mul_action.injective, but that's implicit anyway.

@PatrickMassot PatrickMassot 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 May 8, 2021
@Vierkantor Vierkantor added awaiting-review The author would like community review of the PR and removed awaiting-author A reviewer has asked the author a question or requested changes labels May 10, 2021
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bors d+

I don't know how you want to handle this and #7496, perhaps there's no need to put this one on the queue.

@@ -461,9 +461,17 @@ end add_comm_group

section module

variables {R} [ring R] [add_comm_group M] [module R M] [no_zero_smul_divisors R M]

lemma smul_right_injective {x : M} (hx : x ≠ 0) :
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I must have been imagining that smul_left_injective even exists; I found mul_action.injective, but that's implicit anyway.

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bors bot commented May 10, 2021

✌️ Vierkantor can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

@github-actions github-actions bot added delegated The PR author may merge after reviewing final suggestions. and removed awaiting-review The author would like community review of the PR labels May 10, 2021
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I don't know how you want to handle this and #7496, perhaps there's no need to put this one on the queue.

I expect that will be the case, but I'll keep an eye on it.

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Everything has been merged already, so closing this PR.

@Vierkantor Vierkantor closed this May 11, 2021
@Vierkantor Vierkantor removed the delegated The PR author may merge after reviewing final suggestions. label May 11, 2021
Vierkantor added a commit that referenced this pull request May 11, 2021
…jective M hx`

This is a follow-up PR to #7548.

 * Now that there is also a `smul_right_injective`, we should disambiguate the previous `smul_injective` to `smul_left_injective`.
 * The `M` parameter can't be inferred from arguments before the colon, so we make it explicit.
bors bot pushed a commit that referenced this pull request May 12, 2021
…jective M hx` (#7577)

This is a follow-up PR to #7548.

 * Now that there is also a `smul_right_injective`, we should disambiguate the previous `smul_injective` to `smul_left_injective`.
 * The `M` parameter can't be inferred from arguments before the colon, so we make it explicit in `smul_left_injective` and `smul_right_injective`.
@Vierkantor Vierkantor deleted the smul_right_injective branch October 19, 2021 15:37
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3 participants