```j (]\.&.|. @ ({.&1)) 5 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0 ``` Should give the 5x5 identity matrix. `@` should be fixed (cf. #14). The `&.` should be checked in detail.