import logic inductive category (ob : Type) (mor : ob → ob → Type) : Type := mk : Π (comp : Π⦃A B C : ob⦄, mor B C → mor A B → mor A C) (id : Π {A : ob}, mor A A), (Π {A B C D : ob} {f : mor A B} {g : mor B C} {h : mor C D}, comp h (comp g f) = comp (comp h g) f) → (Π {A B : ob} {f : mor A B}, comp f id = f) → (Π {A B : ob} {f : mor A B}, comp id f = f) → category ob mor class category namespace category section sec_cat parameter A : Type inductive foo := mk : A → foo class foo parameters {ob : Type} {mor : ob → ob → Type} {Cat : category ob mor} definition compose := rec (λ comp id assoc idr idl, comp) Cat definition id := rec (λ comp id assoc idr idl, id) Cat infixr `∘`:60 := compose inductive is_section {A B : ob} (f : mor A B) : Type := mk : ∀g, g ∘ f = id → is_section f end sec_cat end category