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Try doing some basic maths questions in the Lean Theorem Prover. Functions, real numbers, equivalence relations and groups. Click on README.md and then on "Open in CoCalc with one click".

Project: Xena
Views: 18536
License: APACHE
/-
Copyright (c) 2019 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import category_theory.functor_category

namespace category_theory
open category

universes v₁ u₁ -- declare the `v`'s first; see `category_theory.category` for an explanation

variables {C : Type u₁} [𝒞 : category.{v₁} C]
include 𝒞

class monad (T : C ⥤ C) :=
(η : 𝟭 _ ⟶ T)
(μ : T ⋙ T ⟶ T)
(assoc' : ∀ X : C, T.map (nat_trans.app μ X) ≫ μ.app _ = μ.app (T.obj X) ≫ μ.app _ . obviously)
(left_unit' : ∀ X : C, η.app (T.obj X) ≫ μ.app _ = 𝟙 _  . obviously)
(right_unit' : ∀ X : C, T.map (η.app X) ≫ μ.app _ = 𝟙 _  . obviously)

restate_axiom monad.assoc'
restate_axiom monad.left_unit'
restate_axiom monad.right_unit'
attribute [simp] monad.left_unit monad.right_unit

notation `η_` := monad.η
notation `μ_` := monad.μ

end category_theory