fixes agda#2408

Author: jamesmckinna

src/Algebra/Properties/IdempotentCommutativeMonoid.agda

@@ -0,0 +1,38 @@
+------------------------------------------------------------------------
+-- The Agda standard library
+--
+-- Some derivable properties
+------------------------------------------------------------------------
+
+{-# OPTIONS --cubical-compatible --safe #-}
+
+open import Algebra.Bundles using (IdempotentCommutativeMonoid)
+
+module Algebra.Properties.IdempotentCommutativeMonoid
+  {c ℓ} (M : IdempotentCommutativeMonoid c ℓ) where
+
+open IdempotentCommutativeMonoid M
+
+open import Algebra.Consequences.Setoid setoid
+  using (comm∧distrˡ⇒distrʳ; comm∧distrˡ⇒distr)
+open import Algebra.Definitions _≈_
+  using (_DistributesOverˡ_; _DistributesOverʳ_; _DistributesOver_)
+open import Algebra.Properties.CommutativeSemigroup commutativeSemigroup
+  using (interchange)
+open import Relation.Binary.Reasoning.Setoid setoid
+
+
+------------------------------------------------------------------------
+-- Distributivity
+
+distrˡ : _∙_ DistributesOverˡ _∙_
+distrˡ a b c = begin
+    a ∙ (b ∙ c)        ≈⟨ ∙-congʳ (idem a) ⟨
+    (a ∙ a) ∙ (b ∙ c)  ≈⟨ interchange _ _ _ _ ⟩
+    (a ∙ b) ∙ (a ∙ c)  ∎
+
+distrʳ : _∙_ DistributesOverʳ _∙_
+distrʳ = comm∧distrˡ⇒distrʳ ∙-cong comm distrˡ
+
+distr : _∙_ DistributesOver _∙_
+distr = comm∧distrˡ⇒distr ∙-cong comm distrˡ