From 3386254cb6f5fc36c5cb18b7240edde3210a376c Mon Sep 17 00:00:00 2001
From: Jacques Comeaux <jacquesrcomeaux@protonmail.com>
Date: Sun, 4 Jan 2026 16:15:11 -0600
Subject: Add category of symmetric monoidal preorders

---
 Category/Instance/SymMonPre.agda | 73 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 Category/Instance/SymMonPre.agda

(limited to 'Category/Instance/SymMonPre.agda')

diff --git a/Category/Instance/SymMonPre.agda b/Category/Instance/SymMonPre.agda
new file mode 100644
index 0000000..a792c6d
--- /dev/null
+++ b/Category/Instance/SymMonPre.agda
@@ -0,0 +1,73 @@
+{-# OPTIONS --without-K --safe #-}
+
+module Category.Instance.SymMonPre where
+
+import Category.Instance.MonoidalPreorders as MP using (_≗_; module ≗)
+
+open import Categories.Category using (Category)
+open import Categories.Category.Helper using (categoryHelper)
+open import Category.Instance.MonoidalPreorders using (MonoidalPreorders)
+open import Level using (Level; suc; _⊔_)
+open import Preorder.Monoidal using (SymmetricMonoidalPreorder; SymmetricMonoidalMonotone)
+open import Relation.Binary using (IsEquivalence)
+
+private
+
+  identity : {c ℓ e : Level} (A : SymmetricMonoidalPreorder c ℓ e) → SymmetricMonoidalMonotone A A
+  identity {c} {ℓ} {e} A = record
+      { monoidalMonotone = id {monoidalPreorder}
+      }
+    where
+      open SymmetricMonoidalPreorder A using (monoidalPreorder)
+      open Category (MonoidalPreorders c ℓ e) using (id)
+
+  compose
+      : {c ℓ e : Level}
+        {P Q R : SymmetricMonoidalPreorder c ℓ e}
+      → SymmetricMonoidalMonotone Q R
+      → SymmetricMonoidalMonotone P Q
+      → SymmetricMonoidalMonotone P R
+  compose {c} {ℓ} {e} {R = R} G F = record
+      { monoidalMonotone = G.monoidalMonotone ∘ F.monoidalMonotone
+      }
+    where
+      module G = SymmetricMonoidalMonotone G
+      module F = SymmetricMonoidalMonotone F
+      open Category (MonoidalPreorders c ℓ e) using (_∘_)
+
+module _ {c₁ c₂ ℓ₁ ℓ₂ e₁ e₂ : Level} {A : SymmetricMonoidalPreorder c₁ ℓ₁ e₁} {B : SymmetricMonoidalPreorder c₂ ℓ₂ e₂} where
+
+  open SymmetricMonoidalMonotone using () renaming (monoidalMonotone to mM)
+
+  -- Pointwise equality of symmetric monoidal monotone maps
+  _≗_ : (f g : SymmetricMonoidalMonotone A B) → Set (c₁ ⊔ ℓ₂)
+  f ≗ g = mM f MP.≗ mM g
+
+  infix 4 _≗_
+
+  ≗-isEquivalence : IsEquivalence _≗_
+  ≗-isEquivalence = let open MP.≗ in record
+      { refl = λ {x} → refl {x = mM x}
+      ; sym = λ {f g} → sym {x = mM f} {y = mM g}
+      ; trans = λ {f g h} → trans {i = mM f} {j = mM g} {k = mM h}
+      }
+
+  module ≗ = IsEquivalence ≗-isEquivalence
+
+-- The category of symmetric monoidal preorders
+SymMonPre : (c ℓ e : Level) → Category (suc (c ⊔ ℓ ⊔ e)) (c ⊔ ℓ ⊔ e) (c ⊔ ℓ)
+SymMonPre c ℓ e = categoryHelper record
+    { Obj = SymmetricMonoidalPreorder c ℓ e
+    ; _⇒_ = SymmetricMonoidalMonotone
+    ; _≈_ = _≗_
+    ; id  = λ {A} → identity A
+    ; _∘_ = λ {A B C} f g → compose f g
+    ; assoc = λ {_ _ _ D _ _ _ _} → Eq.refl D
+    ; identityˡ = λ {_ B _ _} → Eq.refl B
+    ; identityʳ = λ {_ B _ _} → Eq.refl B
+    ; equiv = ≗-isEquivalence
+    ; ∘-resp-≈ = λ {_ _ C _ h} f≈h g≈i → Eq.trans C f≈h (cong h g≈i)
+    }
+  where
+    open SymmetricMonoidalMonotone using (cong)
+    open SymmetricMonoidalPreorder using (refl; module Eq)
-- 
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