fact: Definition inv_g_of_fx (g f: {ffun 'I_k -> 'I_l}) := if same_codomP f g isn't ReflectT b then finfun id else finfun (fun x => iinv (mem_same_codom b x)).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice finfun) mathcomp(matrix bigop zmodp mxalgebra fingroup) minor