fact: Definition inject_cast n m k E : {ipoly R[n]} -> {ipoly R[k]} := ecast k (_ -> {ipoly R[k]}) E (@inject n m).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(order fingroup perm ssralg zmodp poly ssrint) mathcomp(matrix vector) mathcomp(bigenough) ssrcomplements freeg