import OAI.Algebra.Finitistic.Ordinary.OrdinaryBlockBimodule import OAI.Algebra.Finitistic.Ordinary.OrdinaryAssociativeTensorModules namespace OAI noncomputable section namespace LittleFinitistic.BlockModule universe u /-- A module supported on the first factor of the actual product algebra. -/ def First (_k _L _R Z : Type u) := Z /-- A module supported on the second factor of the actual product algebra. -/ def Second (_k _L _R Z : Type u) := Z variable (k L R Z : Type u) [Field k] [Ring L] [Ring R] [Algebra k L] [Algebra k R] [AddCommGroup Z] [Module k Z] namespace First instance : AddCommGroup (First k L R Z) := inferInstanceAs (AddCommGroup Z) instance : Module k (First k L R Z) := inferInstanceAs (Module k Z) instance [Module L Z] : Module (L × R) (First k L R Z) := Module.compHom Z (RingHom.fst L R) instance [Module L Z] [IsScalarTower k L Z] : IsScalarTower k (L × R) (First k L R Z) where smul_assoc c d z := smul_assoc c d.1 (show Z from z) end First namespace Second instance : AddCommGroup (Second k L R Z) := inferInstanceAs (AddCommGroup Z) instance : Module k (Second k L R Z) := inferInstanceAs (Module k Z) instance [Module R Z] : Module (L × R) (Second k L R Z) := Module.compHom Z (RingHom.snd L R) instance [Module R Z] [IsScalarTower k R Z] : IsScalarTower k (L × R) (Second k L R Z) where smul_assoc c d z := smul_assoc c d.2 (show Z from z) end Second end LittleFinitistic.BlockModule end end OAI