refactor(algebra/monoid_algebra): remove simp from of_apply #13791
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semorrison
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| @@ -1542,11 +1542,11 @@ lemma lift_unique' (F : add_monoid_algebra k G →ₐ[k] A) : | |||
| /-- Decomposition of a `k`-algebra homomorphism from `monoid_algebra k G` by | |||
| its values on `F (single a 1)`. -/ | |||
| lemma lift_unique (F : add_monoid_algebra k G →ₐ[k] A) (f : monoid_algebra k G) : | |||
| F f = f.sum (λ a b, b • F (single a 1)) := | |||
| by conv_lhs { rw lift_unique' F, simp [lift_apply] } | |||
| F f = f.sum (λ a b, b • F (of k G a)) := | |||
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This isn't type correct any more, it needs to be either
Suggested change
| F f = f.sum (λ a b, b • F (of k G a)) := | |
| F f = f.sum (λ a b, b • F (of k G (multiplicative.of_add a))) := |
or
Suggested change
| F f = f.sum (λ a b, b • F (of k G a)) := | |
| F f = f.sum (λ a b, b • F (of' k G a)) := |
eric-wieser
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Apr 29, 2022
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|
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| lemma alg_hom_ext_iff {φ₁ φ₂ : add_monoid_algebra k G →ₐ[k] A} : | ||
| (∀ x, φ₁ (finsupp.single x 1) = φ₂ (finsupp.single x 1)) ↔ φ₁ = φ₂ := | ||
| (∀ x, φ₁ (of k G x) = φ₂ (of k G x)) ↔ φ₁ = φ₂ := |
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This feel slike it will be irritating, because it introduces x : multiplicative G instead of x : G like it used to. Changing from of to of' would fix this.
eric-wieser
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If you remove these simps, then we should:
- add back
[simp]to the lemmas aboutofthat were previously rejected by the linter - copy the
simplemmas below aboutsingleinto versions aboutof
Maybe the second one can wait till a follow-up PR, but I think we should do the first change in this PR.
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I agree, but I may not get to this soon, so I'll leave this PR as |
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I felt that this was unhelpfully "breaking the API" by dropping us down to stuff about
finsupp. On the other hand, the line between monoid_algebra and finsupp remains very murky, so it's not clear this is really an improvement.I'm proposing just this change for now as it would have been helpful for me in other recent work.