fact: Definition directv_def S of phantom {vspace vT} (unwrap (addv_val S)) := \dim (unwrap S) == unwrap (addv_dim S).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)