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[ refactor ] make Relation.Binary.Morphism.Definitions obsolete #2922

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[ refactor ] make Relation.Binary.Morphism.Definitions obsolete #2922

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[ refactor ] make `elation.Binary.Morphism.Definitions` obsolete
jamesmckinna Jan 24, 2026
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Merge branch 'master' into issue2875ptI
jamesmckinna Feb 18, 2026
38634be
deprecate: middle ground, only deprecate names in this release; modul…
jamesmckinna Mar 4, 2026
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Merge branch 'master' into issue2875ptI
jamesmckinna Mar 4, 2026
337b722
refactor: not sure what fixed the problem, but hey?
jamesmckinna Mar 4, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -29,6 +29,9 @@ Minor improvements
properties (and their proofs). In particular, `truncate-irrelevant` is now
deprecated, because definitionally trivial.

* `Relation.Binary.Morphism.Definitions` is no longer imported by any module,
but retained as a stub for compatibility with external users.
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@MatthewDaggitt MatthewDaggitt Mar 3, 2026

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Should it be deprecated then?

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@jamesmckinna jamesmckinna Mar 3, 2026

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Well, see my comment on the module. I'd be happy to, if we no longer have external clients requesting this.

But now I think about it, let's just deprecate anyway?

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@jamesmckinna jamesmckinna Mar 4, 2026 •
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I tried a middle course, deprecating the two names, but not the whole module, but now, against expectations, a warning is raised whenever Function.Definitions.Congruent is used... ???

UPDATED: seemingly fixed now, but let's see what make test does remotely...


* The type of `Relation.Nullary.Negation.Core.contradiction-irr` has been further
weakened so that the negated hypothesis `¬ A` is marked as irrelevant. This is
safe to do, in view of `Relation.Nullary.Recomputable.Properties.¬-recompute`.
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2 changes: 0 additions & 2 deletions src/Algebra/Morphism/Bundles.agda
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Expand Up @@ -16,8 +16,6 @@ open import Algebra.Bundles.Raw using
; RawRingWithoutOne; RawRing)
open import Algebra.Morphism.Structures
open import Level using (Level; suc; _⊔_)
--open import Relation.Binary.Morphism using (IsRelHomomorphism)
--open import Relation.Binary.Morphism.Bundles using (SetoidHomomorphism)
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@MatthewDaggitt MatthewDaggitt Mar 3, 2026

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Delete?

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@jamesmckinna jamesmckinna Mar 3, 2026

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Blast, I thought that I had caught these two.

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@jamesmckinna jamesmckinna Mar 3, 2026

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Wait, won't this PR do the deletion when merged?

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@jamesmckinna jamesmckinna Mar 3, 2026

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And yes, they are commented out (never mind unused) on master, so should be deleted!?


private
variable
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43 changes: 23 additions & 20 deletions src/Algebra/Morphism/Construct/Initial.agda
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Expand Up @@ -17,8 +17,7 @@ module Algebra.Morphism.Construct.Initial {c ℓ : Level} where
open import Algebra.Bundles.Raw using (RawMagma)
open import Algebra.Morphism.Structures
using (IsMagmaHomomorphism; IsMagmaMonomorphism)
open import Function.Definitions using (Injective)
import Relation.Binary.Morphism.Definitions as Rel
open import Function.Definitions using (Congruent; Injective)
open import Relation.Binary.Core using (Rel)

open import Algebra.Construct.Initial {c} {ℓ}
Expand All @@ -27,7 +26,7 @@ private
variable
a m ℓm : Level
A : Set a
≈ : Rel A ℓm


------------------------------------------------------------------------
-- The unique morphism
Expand All @@ -38,25 +37,29 @@ zero ()
------------------------------------------------------------------------
-- Basic properties

cong : (≈ : Rel A ℓm) → Rel.Homomorphic₂ ℤero.Carrier A ℤero._≈_ ≈ zero
cong _ {x = ()}
module _ (≈ : Rel A ℓm) where

cong : Congruent ℤero._≈_ ≈ zero
cong {x = ()}

injective : (≈ : Rel A ℓm) → Injective ℤero._≈_ ≈ zero
injective _ {x = ()}
injective : Injective ℤero._≈_ ≈ zero
injective {x = ()}

------------------------------------------------------------------------
-- Morphism structures

isMagmaHomomorphism : (M : RawMagma m ℓm) →
IsMagmaHomomorphism rawMagma M zero
isMagmaHomomorphism M = record
{ isRelHomomorphism = record { cong = cong (RawMagma._≈_ M) }
; homo = λ()
}

isMagmaMonomorphism : (M : RawMagma m ℓm) →
IsMagmaMonomorphism rawMagma M zero
isMagmaMonomorphism M = record
{ isMagmaHomomorphism = isMagmaHomomorphism M
; injective = injective (RawMagma._≈_ M)
}
module _ (M : RawMagma m ℓm) where

open RawMagma M using (_≈_)

isMagmaHomomorphism : IsMagmaHomomorphism rawMagma M zero
isMagmaHomomorphism = record
{ isRelHomomorphism = record { cong = cong _≈_ }
; homo = λ()
}

isMagmaMonomorphism : IsMagmaMonomorphism rawMagma M zero
isMagmaMonomorphism = record
{ isMagmaHomomorphism = isMagmaHomomorphism
; injective = injective _≈_
}
2 changes: 0 additions & 2 deletions src/Algebra/Morphism/Construct/Terminal.agda
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Expand Up @@ -23,8 +23,6 @@ open import Algebra.Morphism.Structures
; IsRingHomomorphism)
open import Data.Product.Base using (_,_)
open import Function.Definitions using (StrictlySurjective)
import Relation.Binary.Morphism.Definitions as Rel
open import Relation.Binary.Morphism.Structures using (IsRelHomomorphism)

open import Algebra.Construct.Terminal {c} {ℓ}

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1 change: 0 additions & 1 deletion src/Algebra/Morphism/Structures.agda
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Expand Up @@ -13,7 +13,6 @@ open import Algebra.Bundles
import Algebra.Morphism.Definitions as MorphismDefinitions
open import Level using (Level; _⊔_)
open import Function.Definitions using (Injective; Surjective)
open import Relation.Binary.Core using (Rel)
open import Relation.Binary.Morphism.Structures
using (IsRelHomomorphism; IsRelMonomorphism; IsRelIsomorphism)

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7 changes: 4 additions & 3 deletions src/Relation/Binary/Morphism/Bundles.agda
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Expand Up @@ -9,17 +9,18 @@
module Relation.Binary.Morphism.Bundles where

open import Level using (Level; _⊔_)
open import Relation.Binary.Core using (_Preserves_⟶_)
open import Relation.Binary.Bundles using (Setoid; Preorder; Poset)
open import Relation.Binary.Consequences using (mono⇒cong)
open import Relation.Binary.Definitions using (Monotonic₁)
open import Relation.Binary.Morphism.Structures
using (IsRelHomomorphism; IsRelMonomorphism; IsRelIsomorphism
; IsOrderHomomorphism; IsOrderMonomorphism; IsOrderIsomorphism)
open import Relation.Binary.Consequences using (mono⇒cong)

private
variable
ℓ₁ ℓ₂ ℓ₃ ℓ₄ ℓ₅ ℓ₆ : Level


------------------------------------------------------------------------
-- Setoids
------------------------------------------------------------------------
Expand Down Expand Up @@ -96,7 +97,7 @@ module _ (P : Poset ℓ₁ ℓ₂ ℓ₃) (Q : Poset ℓ₄ ℓ₅ ℓ₆) where

-- Smart constructor that automatically constructs the congruence
-- proof from the monotonicity proof
mkPosetHomo : ∀ f → f Preserves P._≤_ ⟶ Q._≤_ → PosetHomomorphism
mkPosetHomo : ∀ f → Monotonic₁ P._≤_ Q._≤_ f → PosetHomomorphism
mkPosetHomo f mono = record
{ ⟦_⟧ = f
; isOrderHomomorphism = record
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15 changes: 4 additions & 11 deletions src/Relation/Binary/Morphism/Definitions.agda
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@@ -1,24 +1,16 @@
------------------------------------------------------------------------
-- The Agda standard library
--
-- Basic definitions for morphisms between algebraic structures
-- Issue #2875: this is a stub module, retained solely for compatibility
------------------------------------------------------------------------

{-# OPTIONS --cubical-compatible --safe #-}

open import Relation.Binary.Core

module Relation.Binary.Morphism.Definitions
{a} (A : Set a) -- The domain of the morphism
{b} (B : Set b) -- The codomain of the morphism
where

open import Level using (Level)

private
variable
ℓ₁ ℓ₂ : Level

------------------------------------------------------------------------
-- Morphism definition in Function.Core

Expand All @@ -28,5 +20,6 @@ open import Function.Core public
------------------------------------------------------------------------
-- Basic definitions

Homomorphic₂ : Rel A ℓ₁ → Rel B ℓ₂ → (A → B) → Set _
Homomorphic₂ _∼₁_ _∼₂_ ⟦_⟧ = ∀ {x y} → x ∼₁ y → ⟦ x ⟧ ∼₂ ⟦ y ⟧
open import Function.Definitions public
using ()
renaming (Congruent to Homomorphic₂)
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@MatthewDaggitt MatthewDaggitt Mar 3, 2026

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If this is a stub module, should we be deprecating Homomorphic₂? Otherwise, where is it going to live?

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@jamesmckinna jamesmckinna Mar 3, 2026 •
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My only reason for not deprecating, is that there seemed to be a request from @pnlph a number of years ago, to retain this name for client compatibility (and hence the public re-export from this module, where it originated). If there is no longer any such demand, then I'd be more radical wrt the surgery being carried out here, and mark the whole module as DEPRECATED...

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@jamesmckinna jamesmckinna Mar 4, 2026

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UPDATED: I've deprecated the lemmas, but not the module, and we'll do that in v3.0

17 changes: 8 additions & 9 deletions src/Relation/Binary/Morphism/Structures.agda
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@@ -1,35 +1,34 @@
------------------------------------------------------------------------
-- The Agda standard library
--
-- Order morphisms
-- Relational morphisms, incl. in particular, order morphisms
------------------------------------------------------------------------

{-# OPTIONS --cubical-compatible --safe #-}

open import Relation.Binary.Core using (Rel)

module Relation.Binary.Morphism.Structures
{a b} {A : Set a} {B : Set b}
where

open import Data.Product.Base using (_,_)
open import Function.Definitions using (Injective; Surjective; Bijective)
open import Function.Definitions
using (Congruent; Injective; Surjective; Bijective)
open import Level using (Level; _⊔_)

open import Relation.Binary.Morphism.Definitions A B
open import Relation.Binary.Core using (Rel)

private
variable
ℓ₁ ℓ₂ ℓ₃ ℓ₄ : Level


------------------------------------------------------------------------
-- Relations
------------------------------------------------------------------------

record IsRelHomomorphism (_∼₁_ : Rel A ℓ₁) (_∼₂_ : Rel B ℓ₂)
(⟦_⟧ : A → B) : Set (a ⊔ ℓ₁ ⊔ ℓ₂) where
field
cong : Homomorphic₂ _∼₁_ _∼₂_ ⟦_⟧
cong : Congruent _∼₁_ _∼₂_ ⟦_⟧


record IsRelMonomorphism (_∼₁_ : Rel A ℓ₁) (_∼₂_ : Rel B ℓ₂)
Expand Down Expand Up @@ -62,8 +61,8 @@ record IsOrderHomomorphism (_≈₁_ : Rel A ℓ₁) (_≈₂_ : Rel B ℓ₂)
(⟦_⟧ : A → B) : Set (a ⊔ ℓ₁ ⊔ ℓ₂ ⊔ ℓ₃ ⊔ ℓ₄)
where
field
cong : Homomorphic₂ _≈₁_ _≈₂_ ⟦_⟧
mono : Homomorphic₂ _≲₁_ _≲₂_ ⟦_⟧
cong : Congruent _≈₁_ _≈₂_ ⟦_⟧
mono : Congruent _≲₁_ _≲₂_ ⟦_⟧

module Eq where
isRelHomomorphism : IsRelHomomorphism _≈₁_ _≈₂_ ⟦_⟧
Expand Down