fact: Definition rswap m n i1 i2 (A : 'M_(m, n)) := \matrix_(i, j) (A (tperm i1 i2 i) j : R).
imports: ssreflect ssrbool ssrfun eqtype ssrnat seq choice fintype finfun bigops ssralg groups perm zmodp morphisms Ring RingClass bigopsClass Setoid Morphisms