category_theory.limits.shapes.kernel_pair

Changes since the initial port

The following section lists changes to this file in mathlib3 and mathlib4 that occured after the initial port. Most recent changes are shown first. Hovering over a commit will show all commits associated with the same mathlib3 commit.

Changes in mathlib3

f6bab678

(last sync)

Changes in mathlib3port

mathlib3

mathlib3port

8ef6f08f

bump to nightly-2024-03-17-08

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

22f01ce4

Diff

@@ -224,8 +224,8 @@ protected theorem pullback {X Y Z A : C} {g : Y ⟶ Z} {a₁ a₂ : A ⟶ Y} (h
 theorem mono_of_isIso_fst (h : IsKernelPair f a b) [IsIso a] : Mono f :=
   by
   obtain ⟨l, h₁, h₂⟩ := limits.pullback_cone.is_limit.lift' h.is_limit (𝟙 _) (𝟙 _) (by simp [h.w])
-  rw [is_pullback.cone_fst, ← is_iso.eq_comp_inv, category.id_comp] at h₁ 
-  rw [h₁, is_iso.inv_comp_eq, category.comp_id] at h₂ 
+  rw [is_pullback.cone_fst, ← is_iso.eq_comp_inv, category.id_comp] at h₁
+  rw [h₁, is_iso.inv_comp_eq, category.comp_id] at h₂
   constructor
   intro Z g₁ g₂ e
   obtain ⟨l', rfl, rfl⟩ := limits.pullback_cone.is_limit.lift' h.is_limit _ _ e

8ef6f08f

bump to nightly-2023-09-24-06

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

5655435f

Diff

@@ -3,9 +3,9 @@ Copyright (c) 2020 Bhavik Mehta. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Bhavik Mehta
 -/
-import Mathbin.CategoryTheory.Limits.Shapes.Equalizers
-import Mathbin.CategoryTheory.Limits.Shapes.CommSq
-import Mathbin.CategoryTheory.Limits.Shapes.RegularMono
+import CategoryTheory.Limits.Shapes.Equalizers
+import CategoryTheory.Limits.Shapes.CommSq
+import CategoryTheory.Limits.Shapes.RegularMono
 
 #align_import category_theory.limits.shapes.kernel_pair from "leanprover-community/mathlib"@"8ef6f08ff8c781c5c07a8b12843710e1a0d8a688"

8ef6f08f

bump to nightly-2023-07-20-09

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

9c56d0dd

Diff

@@ -2,16 +2,13 @@
 Copyright (c) 2020 Bhavik Mehta. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Bhavik Mehta
-
-! This file was ported from Lean 3 source module category_theory.limits.shapes.kernel_pair
-! leanprover-community/mathlib commit 8ef6f08ff8c781c5c07a8b12843710e1a0d8a688
-! Please do not edit these lines, except to modify the commit id
-! if you have ported upstream changes.
 -/
 import Mathbin.CategoryTheory.Limits.Shapes.Equalizers
 import Mathbin.CategoryTheory.Limits.Shapes.CommSq
 import Mathbin.CategoryTheory.Limits.Shapes.RegularMono
 
+#align_import category_theory.limits.shapes.kernel_pair from "leanprover-community/mathlib"@"8ef6f08ff8c781c5c07a8b12843710e1a0d8a688"
+
 /-!
 # Kernel pairs

8ef6f08f

bump to nightly-2023-06-01-16

mathlib commit https://github.com/leanprover-community/mathlib/commit/cca40788df1b8755d5baf17ab2f27dacc2e17acb

b9c87c70

Diff

@@ -67,7 +67,7 @@ namespace IsKernelPair
 
 /-- The data expressing that `(a, b)` is a kernel pair is subsingleton. -/
 instance : Subsingleton (IsKernelPair f a b) :=
-  ⟨fun P Q => by cases P; cases Q; congr ⟩
+  ⟨fun P Q => by cases P; cases Q; congr⟩
 
 #print CategoryTheory.IsKernelPair.id_of_mono /-
 /-- If `f` is a monomorphism, then `(𝟙 _, 𝟙 _)`  is a kernel pair for `f`. -/
@@ -227,8 +227,8 @@ protected theorem pullback {X Y Z A : C} {g : Y ⟶ Z} {a₁ a₂ : A ⟶ Y} (h
 theorem mono_of_isIso_fst (h : IsKernelPair f a b) [IsIso a] : Mono f :=
   by
   obtain ⟨l, h₁, h₂⟩ := limits.pullback_cone.is_limit.lift' h.is_limit (𝟙 _) (𝟙 _) (by simp [h.w])
-  rw [is_pullback.cone_fst, ← is_iso.eq_comp_inv, category.id_comp] at h₁
-  rw [h₁, is_iso.inv_comp_eq, category.comp_id] at h₂
+  rw [is_pullback.cone_fst, ← is_iso.eq_comp_inv, category.id_comp] at h₁ 
+  rw [h₁, is_iso.inv_comp_eq, category.comp_id] at h₂ 
   constructor
   intro Z g₁ g₂ e
   obtain ⟨l', rfl, rfl⟩ := limits.pullback_cone.is_limit.lift' h.is_limit _ _ e

8ef6f08f

bump to nightly-2023-05-28-04

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

6797a637

Diff

@@ -67,10 +67,7 @@ namespace IsKernelPair
 
 /-- The data expressing that `(a, b)` is a kernel pair is subsingleton. -/
 instance : Subsingleton (IsKernelPair f a b) :=
-  ⟨fun P Q => by
-    cases P
-    cases Q
-    congr ⟩
+  ⟨fun P Q => by cases P; cases Q; congr ⟩
 
 #print CategoryTheory.IsKernelPair.id_of_mono /-
 /-- If `f` is a monomorphism, then `(𝟙 _, 𝟙 _)`  is a kernel pair for `f`. -/

8ef6f08f

bump to nightly-2023-03-24-02

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

9cc39ff3

Diff

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Bhavik Mehta
 
 ! This file was ported from Lean 3 source module category_theory.limits.shapes.kernel_pair
-! leanprover-community/mathlib commit f6bab67886fb92c3e2f539cc90a83815f69a189d
+! leanprover-community/mathlib commit 8ef6f08ff8c781c5c07a8b12843710e1a0d8a688
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -15,6 +15,9 @@ import Mathbin.CategoryTheory.Limits.Shapes.RegularMono
 /-!
 # Kernel pairs
 
+> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
+> Any changes to this file require a corresponding PR to mathlib4.
+
 This file defines what it means for a parallel pair of morphisms `a b : R ⟶ X` to be the kernel pair
 for a morphism `f`.
 Some properties of kernel pairs are given, namely allowing one to transfer between

f6bab678

bump to nightly-2023-03-22-16

mathlib commit https://github.com/leanprover-community/mathlib/commit/dd6388c44e6f6b4547070b887c5905d5cfe6c9f8

85865d39

Diff

@@ -46,6 +46,7 @@ variable {C : Type u} [Category.{v} C]
 
 variable {R X Y Z : C} (f : X ⟶ Y) (a b : R ⟶ X)
 
+#print CategoryTheory.IsKernelPair /-
 /-- `is_kernel_pair f a b` expresses that `(a, b)` is a kernel pair for `f`, i.e. `a ≫ f = b ≫ f`
 and the square
   R → X
@@ -57,6 +58,7 @@ This is just an abbreviation for `is_pullback a b f f`.
 abbrev IsKernelPair :=
   IsPullback a b f f
 #align category_theory.is_kernel_pair CategoryTheory.IsKernelPair
+-/
 
 namespace IsKernelPair
 
@@ -67,16 +69,19 @@ instance : Subsingleton (IsKernelPair f a b) :=
     cases Q
     congr ⟩
 
+#print CategoryTheory.IsKernelPair.id_of_mono /-
 /-- If `f` is a monomorphism, then `(𝟙 _, 𝟙 _)`  is a kernel pair for `f`. -/
 theorem id_of_mono [Mono f] : IsKernelPair f (𝟙 _) (𝟙 _) :=
   ⟨⟨rfl⟩, ⟨PullbackCone.isLimitMkIdId _⟩⟩
 #align category_theory.is_kernel_pair.id_of_mono CategoryTheory.IsKernelPair.id_of_mono
+-/
 
 instance [Mono f] : Inhabited (IsKernelPair f (𝟙 _) (𝟙 _)) :=
   ⟨id_of_mono f⟩
 
 variable {f a b}
 
+#print CategoryTheory.IsKernelPair.lift' /-
 /--
 Given a pair of morphisms `p`, `q` to `X` which factor through `f`, they factor through any kernel
 pair of `f`.
@@ -85,7 +90,9 @@ noncomputable def lift' {S : C} (k : IsKernelPair f a b) (p q : S ⟶ X) (w : p
     { t : S ⟶ R // t ≫ a = p ∧ t ≫ b = q } :=
   PullbackCone.IsLimit.lift' k.IsLimit _ _ w
 #align category_theory.is_kernel_pair.lift' CategoryTheory.IsKernelPair.lift'
+-/
 
+#print CategoryTheory.IsKernelPair.cancel_right /-
 /--
 If `(a,b)` is a kernel pair for `f₁ ≫ f₂` and `a ≫ f₁ = b ≫ f₁`, then `(a,b)` is a kernel pair for
 just `f₁`.
@@ -108,7 +115,9 @@ theorem cancel_right {f₁ : X ⟶ Y} {f₂ : Y ⟶ Z} (comm : a ≫ f₁ = b 
           apply m₁.trans (big_k.is_limit.fac s' walking_cospan.left).symm
           apply m₂.trans (big_k.is_limit.fac s' walking_cospan.right).symm⟩ }
 #align category_theory.is_kernel_pair.cancel_right CategoryTheory.IsKernelPair.cancel_right
+-/
 
+#print CategoryTheory.IsKernelPair.cancel_right_of_mono /-
 /-- If `(a,b)` is a kernel pair for `f₁ ≫ f₂` and `f₂` is mono, then `(a,b)` is a kernel pair for
 just `f₁`.
 The converse of `comp_of_mono`.
@@ -117,7 +126,9 @@ theorem cancel_right_of_mono {f₁ : X ⟶ Y} {f₂ : Y ⟶ Z} [Mono f₂]
     (big_k : IsKernelPair (f₁ ≫ f₂) a b) : IsKernelPair f₁ a b :=
   cancel_right (by rw [← cancel_mono f₂, assoc, assoc, big_k.w]) big_k
 #align category_theory.is_kernel_pair.cancel_right_of_mono CategoryTheory.IsKernelPair.cancel_right_of_mono
+-/
 
+#print CategoryTheory.IsKernelPair.comp_of_mono /-
 /--
 If `(a,b)` is a kernel pair for `f₁` and `f₂` is mono, then `(a,b)` is a kernel pair for `f₁ ≫ f₂`.
 The converse of `cancel_right_of_mono`.
@@ -138,7 +149,9 @@ theorem comp_of_mono {f₁ : X ⟶ Y} {f₂ : Y ⟶ Z} [Mono f₂] (small_k : Is
           · exact m₁.trans (pullback_cone.is_limit.lift' small_k.is_limit s.fst s.snd _).2.1.symm
           · exact m₂.trans (pullback_cone.is_limit.lift' small_k.is_limit s.fst s.snd _).2.2.symm⟩ }
 #align category_theory.is_kernel_pair.comp_of_mono CategoryTheory.IsKernelPair.comp_of_mono
+-/
 
+#print CategoryTheory.IsKernelPair.toCoequalizer /-
 /--
 If `(a,b)` is the kernel pair of `f`, and `f` is a coequalizer morphism for some parallel pair, then
 `f` is a coequalizer morphism of `a` and `b`.
@@ -165,7 +178,9 @@ def toCoequalizer (k : IsKernelPair f a b) [r : RegularEpi f] : IsColimit (Cofor
     erw [(cofork.is_colimit.desc' r.is_colimit s.π _).2]
     apply w
 #align category_theory.is_kernel_pair.to_coequalizer CategoryTheory.IsKernelPair.toCoequalizer
+-/
 
+#print CategoryTheory.IsKernelPair.pullback /-
 /-- If `a₁ a₂ : A ⟶ Y` is a kernel pair for `g : Y ⟶ Z`, then `a₁ ×[Z] X` and `a₂ ×[Z] X`
 (`A ×[Z] X ⟶ Y ×[Z] X`) is a kernel pair for `Y ×[Z] X ⟶ X`. -/
 protected theorem pullback {X Y Z A : C} {g : Y ⟶ Z} {a₁ a₂ : A ⟶ Y} (h : IsKernelPair g a₁ a₂)
@@ -206,7 +221,9 @@ protected theorem pullback {X Y Z A : C} {g : Y ⟶ Z} {a₁ a₂ : A ⟶ Y} (h
         · conv_rhs => rw [← h₁, category.assoc, pullback_cone.mk_fst, pullback.lift_snd]
         · conv_rhs => rw [← h₂, category.assoc, pullback_cone.mk_snd, pullback.lift_snd]
 #align category_theory.is_kernel_pair.pullback CategoryTheory.IsKernelPair.pullback
+-/
 
+#print CategoryTheory.IsKernelPair.mono_of_isIso_fst /-
 theorem mono_of_isIso_fst (h : IsKernelPair f a b) [IsIso a] : Mono f :=
   by
   obtain ⟨l, h₁, h₂⟩ := limits.pullback_cone.is_limit.lift' h.is_limit (𝟙 _) (𝟙 _) (by simp [h.w])
@@ -217,7 +234,9 @@ theorem mono_of_isIso_fst (h : IsKernelPair f a b) [IsIso a] : Mono f :=
   obtain ⟨l', rfl, rfl⟩ := limits.pullback_cone.is_limit.lift' h.is_limit _ _ e
   rw [is_pullback.cone_fst, h₂]
 #align category_theory.is_kernel_pair.mono_of_is_iso_fst CategoryTheory.IsKernelPair.mono_of_isIso_fst
+-/
 
+#print CategoryTheory.IsKernelPair.isIso_of_mono /-
 theorem isIso_of_mono (h : IsKernelPair f a b) [Mono f] : IsIso a :=
   by
   rw [←
@@ -227,7 +246,9 @@ theorem isIso_of_mono (h : IsKernelPair f a b) [Mono f] : IsIso a :=
           walking_cospan.left)]
   infer_instance
 #align category_theory.is_kernel_pair.is_iso_of_mono CategoryTheory.IsKernelPair.isIso_of_mono
+-/
 
+#print CategoryTheory.IsKernelPair.of_isIso_of_mono /-
 theorem of_isIso_of_mono [IsIso a] [Mono f] : IsKernelPair f a a :=
   by
   delta is_kernel_pair
@@ -235,6 +256,7 @@ theorem of_isIso_of_mono [IsIso a] [Mono f] : IsKernelPair f a a :=
   · rw [category.comp_id]; · rw [category.id_comp]
   exact (is_pullback.of_horiz_is_iso ⟨rfl⟩).paste_vert (is_kernel_pair.id_of_mono f)
 #align category_theory.is_kernel_pair.of_is_iso_of_mono CategoryTheory.IsKernelPair.of_isIso_of_mono
+-/
 
 end IsKernelPair

f6bab678

bump to nightly-2023-02-27-08

mathlib commit https://github.com/leanprover-community/mathlib/commit/eb0cb4511aaef0da2462207b67358a0e1fe1e2ee

91d8c210

Diff

@@ -233,7 +233,7 @@ theorem of_isIso_of_mono [IsIso a] [Mono f] : IsKernelPair f a a :=
   delta is_kernel_pair
   convert_to is_pullback a (a ≫ 𝟙 X) (𝟙 X ≫ f) f
   · rw [category.comp_id]; · rw [category.id_comp]
-  exact (is_pullback.of_horiz_is_iso ⟨rfl⟩).pasteVert (is_kernel_pair.id_of_mono f)
+  exact (is_pullback.of_horiz_is_iso ⟨rfl⟩).paste_vert (is_kernel_pair.id_of_mono f)
 #align category_theory.is_kernel_pair.of_is_iso_of_mono CategoryTheory.IsKernelPair.of_isIso_of_mono
 
 end IsKernelPair

f6bab678

bump to nightly-2023-02-21-16

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

1107b979

Changes in mathlib4

mathlib3

mathlib4

f6bab678

chore(*): remove empty lines between variable statements (#11418)

Empty lines were removed by executing the following Python script twice

import os
import re


# Loop through each file in the repository
for dir_path, dirs, files in os.walk('.'):
  for filename in files:
    if filename.endswith('.lean'):
      file_path = os.path.join(dir_path, filename)

      # Open the file and read its contents
      with open(file_path, 'r') as file:
        content = file.read()

      # Use a regular expression to replace sequences of "variable" lines separated by empty lines
      # with sequences without empty lines
      modified_content = re.sub(r'(variable.*\n)\n(variable(?! .* in))', r'\1\2', content)

      # Write the modified content back to the file
      with open(file_path, 'w') as file:
        file.write(modified_content)

75c86f04

Diff

@@ -40,7 +40,6 @@ namespace CategoryTheory
 open CategoryTheory CategoryTheory.Category CategoryTheory.Limits
 
 variable {C : Type u} [Category.{v} C]
-
 variable {R X Y Z : C} (f : X ⟶ Y) (a b : R ⟶ X)
 
 /-- `IsKernelPair f a b` expresses that `(a, b)` is a kernel pair for `f`, i.e. `a ≫ f = b ≫ f`

f6bab678

style: homogenise porting notes (#11145)

Homogenises porting notes via capitalisation and addition of whitespace.

It makes the following changes:

converts "--porting note" into "-- Porting note";
converts "porting note" into "Porting note".

8be0b69c

Diff

@@ -74,7 +74,7 @@ instance [Mono f] : Inhabited (IsKernelPair f (𝟙 _) (𝟙 _)) :=
 
 variable {f a b}
 
--- porting note: `lift` and the two following simp lemmas were introduced to ease the port
+-- Porting note: `lift` and the two following simp lemmas were introduced to ease the port
 /--
 Given a pair of morphisms `p`, `q` to `X` which factor through `f`, they factor through any kernel
 pair of `f`.

f6bab678

chore: only four spaces for subsequent lines (#7286)

Co-authored-by: Moritz Firsching <firsching@google.com>

0c7d6fa5

Diff

@@ -85,12 +85,12 @@ noncomputable def lift {S : C} (k : IsKernelPair f a b) (p q : S ⟶ X) (w : p 
 
 @[reassoc (attr := simp)]
 lemma lift_fst {S : C} (k : IsKernelPair f a b) (p q : S ⟶ X) (w : p ≫ f = q ≫ f) :
-  k.lift p q w ≫ a = p :=
+    k.lift p q w ≫ a = p :=
   PullbackCone.IsLimit.lift_fst _ _ _ _
 
 @[reassoc (attr := simp)]
 lemma lift_snd {S : C} (k : IsKernelPair f a b) (p q : S ⟶ X) (w : p ≫ f = q ≫ f) :
-  k.lift p q w ≫ b = q :=
+    k.lift p q w ≫ b = q :=
   PullbackCone.IsLimit.lift_snd _ _ _ _
 
 /--

f6bab678

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

@@ -2,16 +2,13 @@
 Copyright (c) 2020 Bhavik Mehta. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Bhavik Mehta
-
-! This file was ported from Lean 3 source module category_theory.limits.shapes.kernel_pair
-! leanprover-community/mathlib commit f6bab67886fb92c3e2f539cc90a83815f69a189d
-! Please do not edit these lines, except to modify the commit id
-! if you have ported upstream changes.
 -/
 import Mathlib.CategoryTheory.Limits.Shapes.Equalizers
 import Mathlib.CategoryTheory.Limits.Shapes.CommSq
 import Mathlib.CategoryTheory.Limits.Shapes.RegularMono
 
+#align_import category_theory.limits.shapes.kernel_pair from "leanprover-community/mathlib"@"f6bab67886fb92c3e2f539cc90a83815f69a189d"
+
 /-!
 # Kernel pairs

f6bab678

chore: cleanup whitespace (#5988)

Grepping for [^ .:{-] [^ :] and reviewing the results. Once I started I couldn't stop. :-)

Co-authored-by: Scott Morrison <scott.morrison@gmail.com>

12343aa5

Diff

@@ -67,7 +67,7 @@ instance : Subsingleton (IsKernelPair f a b) :=
     cases Q
     congr ⟩
 
-/-- If `f` is a monomorphism, then `(𝟙 _, 𝟙 _)`  is a kernel pair for `f`. -/
+/-- If `f` is a monomorphism, then `(𝟙 _, 𝟙 _)` is a kernel pair for `f`. -/
 theorem id_of_mono [Mono f] : IsKernelPair f (𝟙 _) (𝟙 _) :=
   ⟨⟨rfl⟩, ⟨PullbackCone.isLimitMkIdId _⟩⟩
 #align category_theory.is_kernel_pair.id_of_mono CategoryTheory.IsKernelPair.id_of_mono

f6bab678

chore: fix focusing dots (#5708)

This PR is the result of running

find . -type f -name "*.lean" -exec sed -i -E 's/^( +)\. /\1· /' {} \;
find . -type f -name "*.lean" -exec sed -i -E 'N;s/^( +·)\n +(.*)$/\1 \2/;P;D' {} \;

which firstly replaces . focusing dots with · and secondly removes isolated instances of such dots, unifying them with the following line. A new rule is placed in the style linter to verify this.

cb02d09e

Diff

@@ -122,9 +122,9 @@ theorem cancel_right {f₁ : X ⟶ Y} {f₂ : Y ⟶ Z} (comm : a ≫ f₁ = b 
           big_k.isLimit.fac _ WalkingCospan.right, fun m₁ m₂ => _⟩
         apply big_k.isLimit.hom_ext
         refine' (PullbackCone.mk a b _ : PullbackCone (f₁ ≫ f₂) _).equalizer_ext _ _
-        . apply reassoc_of% comm
-        . apply m₁.trans (big_k.isLimit.fac s' WalkingCospan.left).symm
-        . apply m₂.trans (big_k.isLimit.fac s' WalkingCospan.right).symm⟩ }
+        · apply reassoc_of% comm
+        · apply m₁.trans (big_k.isLimit.fac s' WalkingCospan.left).symm
+        · apply m₂.trans (big_k.isLimit.fac s' WalkingCospan.right).symm⟩ }
 #align category_theory.is_kernel_pair.cancel_right CategoryTheory.IsKernelPair.cancel_right
 
 /-- If `(a,b)` is a kernel pair for `f₁ ≫ f₂` and `f₂` is mono, then `(a,b)` is a kernel pair for
@@ -147,11 +147,11 @@ theorem comp_of_mono {f₁ : X ⟶ Y} {f₂ : Y ⟶ Z} [Mono f₂] (small_k : Is
       refine' PullbackCone.isLimitAux _
         (fun s => small_k.lift s.fst s.snd (by rw [← cancel_mono f₂, assoc, s.condition, assoc]))
         (by simp) (by simp) _
-      . intro s m hm
+      · intro s m hm
         apply small_k.isLimit.hom_ext
         apply PullbackCone.equalizer_ext small_k.cone _ _
-        . exact (hm WalkingCospan.left).trans (by simp)
-        . exact (hm WalkingCospan.right).trans (by simp)⟩ }
+        · exact (hm WalkingCospan.left).trans (by simp)
+        · exact (hm WalkingCospan.right).trans (by simp)⟩ }
 #align category_theory.is_kernel_pair.comp_of_mono CategoryTheory.IsKernelPair.comp_of_mono
 
 /--
@@ -166,8 +166,8 @@ def toCoequalizer (k : IsKernelPair f a b) [r : RegularEpi f] : IsColimit (Cofor
     (fun s => Cofork.IsColimit.desc r.isColimit s.π
       (by rw [← ht, assoc, s.condition, reassoc_of% kt]))
     (fun s => _) (fun s m w => _)
-  . apply Cofork.IsColimit.π_desc' r.isColimit
-  . apply Cofork.IsColimit.hom_ext r.isColimit
+  · apply Cofork.IsColimit.π_desc' r.isColimit
+  · apply Cofork.IsColimit.hom_ext r.isColimit
     exact w.trans (Cofork.IsColimit.π_desc' r.isColimit _ _).symm
 #align category_theory.is_kernel_pair.to_coequalizer CategoryTheory.IsKernelPair.toCoequalizer
 
@@ -182,17 +182,17 @@ protected theorem pullback {X Y Z A : C} {g : Y ⟶ Z} {a₁ a₂ : A ⟶ Y} (h
     (fun s => pullback.lift (s.fst ≫ pullback.fst)
       (h.lift (s.fst ≫ pullback.snd) (s.snd ≫ pullback.snd) _ ) _) (fun s => _) (fun s => _)
         (fun s m hm => _)⟩⟩
-  . simp_rw [Category.assoc, ← pullback.condition, ← Category.assoc, s.condition]
-  . simp only [assoc, lift_fst_assoc, pullback.condition]
-  . ext <;> simp
-  . ext
-    . simp [s.condition]
-    . simp
-  . apply pullback.hom_ext
-    . simpa using hm WalkingCospan.left =≫ pullback.fst
-    . apply PullbackCone.IsLimit.hom_ext h.isLimit
-      . simpa using hm WalkingCospan.left =≫ pullback.snd
-      . simpa using hm WalkingCospan.right =≫ pullback.snd
+  · simp_rw [Category.assoc, ← pullback.condition, ← Category.assoc, s.condition]
+  · simp only [assoc, lift_fst_assoc, pullback.condition]
+  · ext <;> simp
+  · ext
+    · simp [s.condition]
+    · simp
+  · apply pullback.hom_ext
+    · simpa using hm WalkingCospan.left =≫ pullback.fst
+    · apply PullbackCone.IsLimit.hom_ext h.isLimit
+      · simpa using hm WalkingCospan.left =≫ pullback.snd
+      · simpa using hm WalkingCospan.right =≫ pullback.snd
 #align category_theory.is_kernel_pair.pullback CategoryTheory.IsKernelPair.pullback
 
 theorem mono_of_isIso_fst (h : IsKernelPair f a b) [IsIso a] : Mono f := by

f6bab678

feat: more consistent use of ext, and updating porting notes. (#5242)

Co-authored-by: Scott Morrison <scott.morrison@anu.edu.au>

dbae2f17

Diff

@@ -184,8 +184,8 @@ protected theorem pullback {X Y Z A : C} {g : Y ⟶ Z} {a₁ a₂ : A ⟶ Y} (h
         (fun s m hm => _)⟩⟩
   . simp_rw [Category.assoc, ← pullback.condition, ← Category.assoc, s.condition]
   . simp only [assoc, lift_fst_assoc, pullback.condition]
-  . apply pullback.hom_ext <;> simp
-  . apply pullback.hom_ext
+  . ext <;> simp
+  . ext
     . simp [s.condition]
     . simp
   . apply pullback.hom_ext

f6bab678

chore: bye-bye, solo bys! (#3825)

This PR puts, with one exception, every single remaining by that lies all by itself on its own line to the previous line, thus matching the current behaviour of start-port.sh. The exception is when the by begins the second or later argument to a tuple or anonymous constructor; see https://github.com/leanprover-community/mathlib4/pull/3825#discussion_r1186702599.

Essentially this is s/\n *by$/ by/g, but with manual editing to satisfy the linter's max-100-char-line requirement. The Python style linter is also modified to catch these "isolated bys".

14167e48

Diff

@@ -115,18 +115,16 @@ theorem cancel_right {f₁ : X ⟶ Y} {f₂ : Y ⟶ Z} (comm : a ≫ f₁ = b 
     (big_k : IsKernelPair (f₁ ≫ f₂) a b) : IsKernelPair f₁ a b :=
   { w := comm
     isLimit' :=
-      ⟨PullbackCone.isLimitAux' _ fun s =>
-          by
-          let s' : PullbackCone (f₁ ≫ f₂) (f₁ ≫ f₂) :=
-            PullbackCone.mk s.fst s.snd (s.condition_assoc _)
-          refine'
-            ⟨big_k.isLimit.lift s', big_k.isLimit.fac _ WalkingCospan.left,
-              big_k.isLimit.fac _ WalkingCospan.right, fun m₁ m₂ => _⟩
-          apply big_k.isLimit.hom_ext
-          refine' (PullbackCone.mk a b _ : PullbackCone (f₁ ≫ f₂) _).equalizer_ext _ _
-          . apply reassoc_of% comm
-          . apply m₁.trans (big_k.isLimit.fac s' WalkingCospan.left).symm
-          . apply m₂.trans (big_k.isLimit.fac s' WalkingCospan.right).symm⟩ }
+      ⟨PullbackCone.isLimitAux' _ fun s => by
+        let s' : PullbackCone (f₁ ≫ f₂) (f₁ ≫ f₂) :=
+          PullbackCone.mk s.fst s.snd (s.condition_assoc _)
+        refine' ⟨big_k.isLimit.lift s', big_k.isLimit.fac _ WalkingCospan.left,
+          big_k.isLimit.fac _ WalkingCospan.right, fun m₁ m₂ => _⟩
+        apply big_k.isLimit.hom_ext
+        refine' (PullbackCone.mk a b _ : PullbackCone (f₁ ≫ f₂) _).equalizer_ext _ _
+        . apply reassoc_of% comm
+        . apply m₁.trans (big_k.isLimit.fac s' WalkingCospan.left).symm
+        . apply m₂.trans (big_k.isLimit.fac s' WalkingCospan.right).symm⟩ }
 #align category_theory.is_kernel_pair.cancel_right CategoryTheory.IsKernelPair.cancel_right
 
 /-- If `(a,b)` is a kernel pair for `f₁ ≫ f₂` and `f₂` is mono, then `(a,b)` is a kernel pair for

f6bab678

feat: port CategoryTheory.Limits.Shapes.KernelPair (#2871)

1bd50665

`category_theory.limits.shapes.kernel_pair` ⟷ `Mathlib.CategoryTheory.Limits.Shapes.KernelPair`

Changes since the initial port

Changes in mathlib3

Changes in mathlib3port

Changes in mathlib4

Dependencies 2 + 252

category_theory.limits.shapes.kernel_pair ⟷ Mathlib.CategoryTheory.Limits.Shapes.KernelPair

Changes since the initial port

Changes in mathlib3

Changes in mathlib3port

Changes in mathlib4

Dependencies 2 + 252

`category_theory.limits.shapes.kernel_pair` ⟷ `Mathlib.CategoryTheory.Limits.Shapes.KernelPair`