data.zmod.algebra | Mathlib porting status

(last sync)

chore(data/zmod/algebra): make zmod.algebra a def (#19197)

zmod.algebra creates a diamond about the zmod p-algebra structure on zmod p:

import algebra.algebra.basic
import data.zmod.algebra

example (p : ℕ) : algebra.id (zmod p) =
  (zmod.algebra (zmod p) p) := rfl --fails

This is also causing troubles with the port. We turn zmod.algebra into a def.

Diff

@@ -24,7 +24,9 @@ instance (p : ℕ) : subsingleton (algebra (zmod p) R) :=
 section
 variables {n : ℕ} (m : ℕ) [char_p R m]
 
-/-- The `zmod n`-algebra structure on rings whose characteristic `m` divides `n` -/
+/-- The `zmod n`-algebra structure on rings whose characteristic `m` divides `n`.
+See note [reducible non-instances]. -/
+@[reducible]
 def algebra' (h : m ∣ n) : algebra (zmod n) R :=
 { smul := λ a r, a * r,
   commutes' := λ a r, show (a * r : R) = r * a,
@@ -39,6 +41,10 @@ def algebra' (h : m ∣ n) : algebra (zmod n) R :=
 
 end
 
-instance (p : ℕ) [char_p R p] : algebra (zmod p) R := algebra' R p dvd_rfl
+/-- The `zmod p`-algebra structure on a ring of characteristic `p`. This is not an
+instance since it creates a diamond with `algebra.id`.
+See note [reducible non-instances]. -/
+@[reducible]
+def algebra (p : ℕ) [char_p R p] : algebra (zmod p) R := algebra' R p dvd_rfl
 
 end zmod

(first ported)

Changes in mathlib3port

mathlib3

mathlib3port

bump to nightly-2024-04-19-08

mathlib commit https://github.com/leanprover-community/mathlib/commit/65a1391a0106c9204fe45bc73a039f056558cb83

a9e81450

Diff

@@ -37,7 +37,7 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
     commutes' := fun a r =>
       show (a * r : R) = r * a
         by
-        rcases ZMod.int_cast_surjective a with ⟨k, rfl⟩
+        rcases ZMod.intCast_surjective a with ⟨k, rfl⟩
         show ZMod.castHom h R k * r = r * ZMod.castHom h R k
         rw [map_intCast]
         exact Commute.cast_int_left r k

bump to nightly-2024-04-06-08

mathlib commit https://github.com/leanprover-community/mathlib/commit/65a1391a0106c9204fe45bc73a039f056558cb83

e34029c9

Diff

@@ -3,7 +3,7 @@ Copyright (c) 2021 Johan Commelin. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Johan Commelin
 -/
-import Data.Zmod.Basic
+import Data.ZMod.Basic
 import Algebra.Algebra.Basic
 
 #align_import data.zmod.algebra from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"

bump to nightly-2023-09-24-06

mathlib commit https://github.com/leanprover-community/mathlib/commit/ce64cd319bb6b3e82f31c2d38e79080d377be451

5655435f

Diff

@@ -3,8 +3,8 @@ Copyright (c) 2021 Johan Commelin. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Johan Commelin
 -/
-import Mathbin.Data.Zmod.Basic
-import Mathbin.Algebra.Algebra.Basic
+import Data.Zmod.Basic
+import Algebra.Algebra.Basic
 
 #align_import data.zmod.algebra from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"

bump to nightly-2023-07-20-09

mathlib commit https://github.com/leanprover-community/mathlib/commit/8ea5598db6caeddde6cb734aa179cc2408dbd345

9c56d0dd

Diff

@@ -2,15 +2,12 @@
 Copyright (c) 2021 Johan Commelin. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Johan Commelin
-
-! This file was ported from Lean 3 source module data.zmod.algebra
-! leanprover-community/mathlib commit 0723536a0522d24fc2f159a096fb3304bef77472
-! Please do not edit these lines, except to modify the commit id
-! if you have ported upstream changes.
 -/
 import Mathbin.Data.Zmod.Basic
 import Mathbin.Algebra.Algebra.Basic
 
+#align_import data.zmod.algebra from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"
+
 /-!
 # The `zmod n`-algebra structure on rings whose characteristic divides `n`

bump to nightly-2023-06-21-15

mathlib commit https://github.com/leanprover-community/mathlib/commit/f2ad3645af9effcdb587637dc28a6074edc813f9

3f5dfaa8

Diff

@@ -50,6 +50,7 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
 
 end
 
+#print ZMod.algebra /-
 /-- The `zmod p`-algebra structure on a ring of characteristic `p`. This is not an
 instance since it creates a diamond with `algebra.id`.
 See note [reducible non-instances]. -/
@@ -57,6 +58,7 @@ See note [reducible non-instances]. -/
 def algebra (p : ℕ) [CharP R p] : Algebra (ZMod p) R :=
   algebra' R p dvd_rfl
 #align zmod.algebra ZMod.algebra
+-/
 
 end ZMod

bump to nightly-2023-06-20-03

mathlib commit https://github.com/leanprover-community/mathlib/commit/0723536a0522d24fc2f159a096fb3304bef77472

1fb3229c

Diff

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Johan Commelin
 
 ! This file was ported from Lean 3 source module data.zmod.algebra
-! leanprover-community/mathlib commit 290a7ba01fbcab1b64757bdaa270d28f4dcede35
+! leanprover-community/mathlib commit 0723536a0522d24fc2f159a096fb3304bef77472
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -31,7 +31,9 @@ section
 variable {n : ℕ} (m : ℕ) [CharP R m]
 
 #print ZMod.algebra' /-
-/-- The `zmod n`-algebra structure on rings whose characteristic `m` divides `n` -/
+/-- The `zmod n`-algebra structure on rings whose characteristic `m` divides `n`.
+See note [reducible non-instances]. -/
+@[reducible]
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with
     smul := fun a r => a * r
@@ -48,8 +50,13 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
 
 end
 
-instance (p : ℕ) [CharP R p] : Algebra (ZMod p) R :=
+/-- The `zmod p`-algebra structure on a ring of characteristic `p`. This is not an
+instance since it creates a diamond with `algebra.id`.
+See note [reducible non-instances]. -/
+@[reducible]
+def algebra (p : ℕ) [CharP R p] : Algebra (ZMod p) R :=
   algebra' R p dvd_rfl
+#align zmod.algebra ZMod.algebra
 
 end ZMod

bump to nightly-2023-06-13-21

mathlib commit https://github.com/leanprover-community/mathlib/commit/9fb8964792b4237dac6200193a0d533f1b3f7423

829520ac

Diff

@@ -30,6 +30,7 @@ section
 
 variable {n : ℕ} (m : ℕ) [CharP R m]
 
+#print ZMod.algebra' /-
 /-- The `zmod n`-algebra structure on rings whose characteristic `m` divides `n` -/
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with
@@ -43,6 +44,7 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
         exact Commute.cast_int_left r k
     smul_def' := fun a r => rfl }
 #align zmod.algebra' ZMod.algebra'
+-/
 
 end

bump to nightly-2023-05-28-06

mathlib commit https://github.com/leanprover-community/mathlib/commit/917c3c072e487b3cccdbfeff17e75b40e45f66cb

ba5d8b97

Diff

@@ -30,12 +30,6 @@ section
 
 variable {n : ℕ} (m : ℕ) [CharP R m]
 
-/- warning: zmod.algebra' -> ZMod.algebra' is a dubious translation:
-lean 3 declaration is
-  forall (R : Type.{u1}) [_inst_1 : Ring.{u1} R] {n : Nat} (m : Nat) [_inst_2 : CharP.{u1} R (AddGroupWithOne.toAddMonoidWithOne.{u1} R (AddCommGroupWithOne.toAddGroupWithOne.{u1} R (Ring.toAddCommGroupWithOne.{u1} R _inst_1))) m], (Dvd.Dvd.{0} Nat Nat.hasDvd m n) -> (Algebra.{0, u1} (ZMod n) R (CommRing.toCommSemiring.{0} (ZMod n) (ZMod.commRing n)) (Ring.toSemiring.{u1} R _inst_1))
-but is expected to have type
-  forall (R : Type.{u1}) [_inst_1 : Ring.{u1} R] {n : Nat} (m : Nat) [_inst_2 : CharP.{u1} R (AddGroupWithOne.toAddMonoidWithOne.{u1} R (Ring.toAddGroupWithOne.{u1} R _inst_1)) m], (Dvd.dvd.{0} Nat Nat.instDvdNat m n) -> (Algebra.{0, u1} (ZMod n) R (CommRing.toCommSemiring.{0} (ZMod n) (ZMod.commRing n)) (Ring.toSemiring.{u1} R _inst_1))
-Case conversion may be inaccurate. Consider using '#align zmod.algebra' ZMod.algebra'ₓ'. -/
 /-- The `zmod n`-algebra structure on rings whose characteristic `m` divides `n` -/
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with

bump to nightly-2023-03-27-02

mathlib commit https://github.com/leanprover-community/mathlib/commit/ce86f4e05e9a9b8da5e316b22c76ce76440c56a1

0e4ebd8c

Diff

@@ -32,7 +32,7 @@ variable {n : ℕ} (m : ℕ) [CharP R m]
 
 /- warning: zmod.algebra' -> ZMod.algebra' is a dubious translation:
 lean 3 declaration is
-  forall (R : Type.{u1}) [_inst_1 : Ring.{u1} R] {n : Nat} (m : Nat) [_inst_2 : CharP.{u1} R (AddGroupWithOne.toAddMonoidWithOne.{u1} R (NonAssocRing.toAddGroupWithOne.{u1} R (Ring.toNonAssocRing.{u1} R _inst_1))) m], (Dvd.Dvd.{0} Nat Nat.hasDvd m n) -> (Algebra.{0, u1} (ZMod n) R (CommRing.toCommSemiring.{0} (ZMod n) (ZMod.commRing n)) (Ring.toSemiring.{u1} R _inst_1))
+  forall (R : Type.{u1}) [_inst_1 : Ring.{u1} R] {n : Nat} (m : Nat) [_inst_2 : CharP.{u1} R (AddGroupWithOne.toAddMonoidWithOne.{u1} R (AddCommGroupWithOne.toAddGroupWithOne.{u1} R (Ring.toAddCommGroupWithOne.{u1} R _inst_1))) m], (Dvd.Dvd.{0} Nat Nat.hasDvd m n) -> (Algebra.{0, u1} (ZMod n) R (CommRing.toCommSemiring.{0} (ZMod n) (ZMod.commRing n)) (Ring.toSemiring.{u1} R _inst_1))
 but is expected to have type
   forall (R : Type.{u1}) [_inst_1 : Ring.{u1} R] {n : Nat} (m : Nat) [_inst_2 : CharP.{u1} R (AddGroupWithOne.toAddMonoidWithOne.{u1} R (Ring.toAddGroupWithOne.{u1} R _inst_1)) m], (Dvd.dvd.{0} Nat Nat.instDvdNat m n) -> (Algebra.{0, u1} (ZMod n) R (CommRing.toCommSemiring.{0} (ZMod n) (ZMod.commRing n)) (Ring.toSemiring.{u1} R _inst_1))
 Case conversion may be inaccurate. Consider using '#align zmod.algebra' ZMod.algebra'ₓ'. -/

bump to nightly-2023-03-24-22

mathlib commit https://github.com/leanprover-community/mathlib/commit/b19481deb571022990f1baa9cbf9172e6757a479

6eace303

Diff

@@ -30,7 +30,12 @@ section
 
 variable {n : ℕ} (m : ℕ) [CharP R m]
 
-#print ZMod.algebra' /-
+/- warning: zmod.algebra' -> ZMod.algebra' is a dubious translation:
+lean 3 declaration is
+  forall (R : Type.{u1}) [_inst_1 : Ring.{u1} R] {n : Nat} (m : Nat) [_inst_2 : CharP.{u1} R (AddGroupWithOne.toAddMonoidWithOne.{u1} R (NonAssocRing.toAddGroupWithOne.{u1} R (Ring.toNonAssocRing.{u1} R _inst_1))) m], (Dvd.Dvd.{0} Nat Nat.hasDvd m n) -> (Algebra.{0, u1} (ZMod n) R (CommRing.toCommSemiring.{0} (ZMod n) (ZMod.commRing n)) (Ring.toSemiring.{u1} R _inst_1))
+but is expected to have type
+  forall (R : Type.{u1}) [_inst_1 : Ring.{u1} R] {n : Nat} (m : Nat) [_inst_2 : CharP.{u1} R (AddGroupWithOne.toAddMonoidWithOne.{u1} R (Ring.toAddGroupWithOne.{u1} R _inst_1)) m], (Dvd.dvd.{0} Nat Nat.instDvdNat m n) -> (Algebra.{0, u1} (ZMod n) R (CommRing.toCommSemiring.{0} (ZMod n) (ZMod.commRing n)) (Ring.toSemiring.{u1} R _inst_1))
+Case conversion may be inaccurate. Consider using '#align zmod.algebra' ZMod.algebra'ₓ'. -/
 /-- The `zmod n`-algebra structure on rings whose characteristic `m` divides `n` -/
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with
@@ -44,7 +49,6 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
         exact Commute.cast_int_left r k
     smul_def' := fun a r => rfl }
 #align zmod.algebra' ZMod.algebra'
--/
 
 end

bump to nightly-2023-03-21-02

mathlib commit https://github.com/leanprover-community/mathlib/commit/290a7ba01fbcab1b64757bdaa270d28f4dcede35

c67df486

Diff

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Johan Commelin
 
 ! This file was ported from Lean 3 source module data.zmod.algebra
-! leanprover-community/mathlib commit 972aa4234fa56ce119d19506045158a9d76881fd
+! leanprover-community/mathlib commit 290a7ba01fbcab1b64757bdaa270d28f4dcede35
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -13,6 +13,9 @@ import Mathbin.Algebra.Algebra.Basic
 
 /-!
 # The `zmod n`-algebra structure on rings whose characteristic divides `n`
+
+> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
+> Any changes to this file require a corresponding PR to mathlib4.
 -/

bump to nightly-2023-03-19-18

mathlib commit https://github.com/leanprover-community/mathlib/commit/1f4705ccdfe1e557fc54a0ce081a05e33d2e6240

a0aedb66

Diff

@@ -27,6 +27,7 @@ section
 
 variable {n : ℕ} (m : ℕ) [CharP R m]
 
+#print ZMod.algebra' /-
 /-- The `zmod n`-algebra structure on rings whose characteristic `m` divides `n` -/
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with
@@ -40,6 +41,7 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
         exact Commute.cast_int_left r k
     smul_def' := fun a r => rfl }
 #align zmod.algebra' ZMod.algebra'
+-/
 
 end

bump to nightly-2023-02-21-16

mathlib commit https://github.com/leanprover-community/mathlib/commit/bd9851ca476957ea4549eb19b40e7b5ade9428cc

1107b979

Changes in mathlib4

mathlib3

mathlib4

chore: split Algebra.Algebra.Basic (#12486)

Splits Algebra.Algebra.Defs off Algebra.Algebra.Basic. Most imports only need the Defs file, which has significantly smaller imports. The remaining Algebra.Algebra.Basic is now a grab-bag of unrelated results, and should probably be split further or rehomed.

This is mostly motivated by the wasted effort during minimization upon encountering Algebra.Algebra.Basic.

Co-authored-by: Scott Morrison <scott.morrison@gmail.com> Co-authored-by: Ruben Van de Velde <65514131+Ruben-VandeVelde@users.noreply.github.com>

d64b17d9

Diff

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Johan Commelin
 -/
 import Mathlib.Data.ZMod.Basic
-import Mathlib.Algebra.Algebra.Basic
+import Mathlib.Algebra.Algebra.Defs
 
 #align_import data.zmod.algebra from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"

chore: Rename nat_cast/int_cast/rat_cast to natCast/intCast/ratCast (#11486)

Now that I am defining NNRat.cast, I want a definitive answer to this naming issue. Plenty of lemmas in mathlib already use natCast/intCast/ratCast over nat_cast/int_cast/rat_cast, and this matches with the general expectation that underscore-separated name parts correspond to a single declaration.

145460b9

Diff

@@ -32,7 +32,7 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
     smul := fun a r => cast a * r
     commutes' := fun a r =>
       show (cast a * r : R) = r * cast a by
-        rcases ZMod.int_cast_surjective a with ⟨k, rfl⟩
+        rcases ZMod.intCast_surjective a with ⟨k, rfl⟩
         show ZMod.castHom h R k * r = r * ZMod.castHom h R k
         rw [map_intCast, Int.cast_comm]
     smul_def' := fun a r => rfl }

refactor(ZMod): remove coe out of ZMod (#9839)

Co-authored-by: Ruben Van de Velde <65514131+Ruben-VandeVelde@users.noreply.github.com> Co-authored-by: Vierkantor <vierkantor@vierkantor.com>

c27bc4e1

Diff

@@ -29,9 +29,9 @@ See note [reducible non-instances]. -/
 @[reducible]
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with
-    smul := fun a r => a * r
+    smul := fun a r => cast a * r
     commutes' := fun a r =>
-      show (a * r : R) = r * a by
+      show (cast a * r : R) = r * cast a by
         rcases ZMod.int_cast_surjective a with ⟨k, rfl⟩
         show ZMod.castHom h R k * r = r * ZMod.castHom h R k
         rw [map_intCast, Int.cast_comm]

chore: Move Int and Nat cast lemmas (#9503)

Part of #9411

e1b05c51

Diff

@@ -34,8 +34,7 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
       show (a * r : R) = r * a by
         rcases ZMod.int_cast_surjective a with ⟨k, rfl⟩
         show ZMod.castHom h R k * r = r * ZMod.castHom h R k
-        rw [map_intCast]
-        exact Commute.cast_int_left r k
+        rw [map_intCast, Int.cast_comm]
     smul_def' := fun a r => rfl }
 #align zmod.algebra' ZMod.algebra'

chore: banish Type _ and Sort _ (#6499)

We remove all possible occurences of Type _ and Sort _ in favor of Type* and Sort*.

This has nice performance benefits.

32de3f67

Diff

@@ -15,7 +15,7 @@ import Mathlib.Algebra.Algebra.Basic
 
 namespace ZMod
 
-variable (R : Type _) [Ring R]
+variable (R : Type*) [Ring R]
 
 instance (p : ℕ) : Subsingleton (Algebra (ZMod p) R) :=
   ⟨fun _ _ => Algebra.algebra_ext _ _ <| RingHom.congr_fun <| Subsingleton.elim _ _⟩

chore: script to replace headers with #align_import statements (#5979)

depends on: #5966

Co-authored-by: Eric Wieser <wieser.eric@gmail.com> Co-authored-by: Scott Morrison <scott.morrison@gmail.com>

89aa3a3b

Diff

@@ -2,15 +2,12 @@
 Copyright (c) 2021 Johan Commelin. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Johan Commelin
-
-! This file was ported from Lean 3 source module data.zmod.algebra
-! leanprover-community/mathlib commit 0723536a0522d24fc2f159a096fb3304bef77472
-! Please do not edit these lines, except to modify the commit id
-! if you have ported upstream changes.
 -/
 import Mathlib.Data.ZMod.Basic
 import Mathlib.Algebra.Algebra.Basic
 
+#align_import data.zmod.algebra from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"
+
 /-!
 # The `ZMod n`-algebra structure on rings whose characteristic divides `n`
 -/

forward port leanprover-community/mathlib#19197 (#5284)

aa4f7c81

Diff

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Johan Commelin
 
 ! This file was ported from Lean 3 source module data.zmod.algebra
-! leanprover-community/mathlib commit 972aa4234fa56ce119d19506045158a9d76881fd
+! leanprover-community/mathlib commit 0723536a0522d24fc2f159a096fb3304bef77472
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -27,7 +27,9 @@ section
 
 variable {n : ℕ} (m : ℕ) [CharP R m]
 
-/-- The `ZMod n`-algebra structure on rings whose characteristic `m` divides `n` -/
+/-- The `ZMod n`-algebra structure on rings whose characteristic `m` divides `n`.
+See note [reducible non-instances]. -/
+@[reducible]
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with
     smul := fun a r => a * r
@@ -42,7 +44,12 @@ def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
 
 end
 
-instance (p : ℕ) [CharP R p] : Algebra (ZMod p) R :=
+/-- The `zmod p`-algebra structure on a ring of characteristic `p`. This is not an
+instance since it creates a diamond with `algebra.id`.
+See note [reducible non-instances]. -/
+@[reducible]
+def algebra (p : ℕ) [CharP R p] : Algebra (ZMod p) R :=
   algebra' R p dvd_rfl
+#align zmod.algebra ZMod.algebra
 
 end ZMod

chore: reenable eta, bump to nightly 2023-05-16 (#3414)

Now that leanprover/lean4#2210 has been merged, this PR:

removes all the set_option synthInstance.etaExperiment true commands (and some etaExperiment% term elaborators)
removes many but not quite all set_option maxHeartbeats commands
makes various other changes required to cope with leanprover/lean4#2210.

Co-authored-by: Scott Morrison <scott.morrison@anu.edu.au> Co-authored-by: Scott Morrison <scott.morrison@gmail.com> Co-authored-by: Matthew Ballard <matt@mrb.email>

a6e1045f

Diff

@@ -27,7 +27,6 @@ section
 
 variable {n : ℕ} (m : ℕ) [CharP R m]
 
-set_option synthInstance.etaExperiment true in
 /-- The `ZMod n`-algebra structure on rings whose characteristic `m` divides `n` -/
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with

chore(*): tweak priorities for linear algebra (#3840)

We make sure that the canonical path from NonAssocSemiring to Ring passes through Semiring, as this is a path which is followed all the time in linear algebra where the defining semilinear map σ : R →+* S depends on the NonAssocSemiring structure of R and S while the module definition depends on the Semiring structure.

Tt is not currently possible to adjust priorities by hand (see lean4#2115). Instead, the last declared instance is used, so we make sure that Semiring is declared after NonAssocRing, so that Semiring -> NonAssocSemiring is tried before NonAssocRing -> NonAssocSemiring.

0d22228a

Diff

@@ -27,6 +27,7 @@ section
 
 variable {n : ℕ} (m : ℕ) [CharP R m]
 
+set_option synthInstance.etaExperiment true in
 /-- The `ZMod n`-algebra structure on rings whose characteristic `m` divides `n` -/
 def algebra' (h : m ∣ n) : Algebra (ZMod n) R :=
   { ZMod.castHom h R with