fact: Definition equivalent m1 n1 m2 n2 (A : 'M[R]_(m1,n1)) (B : 'M[R]_(m2,n2)) := [/\ m1 = m2, n1 = n2 & exists M N, [/\ M \in unitmx, N \in unitmx & M *m A *m N = conform_mx A B]].
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype fintype finfun ssrnat seq) mathcomp(choice ssralg poly polydiv mxpoly matrix bigop) mathcomp(mxalgebra perm fingroup tuple) mxstructure dvdring