ref: f1b64c623980598b81414f35c2d95c8d8ff7425a dir: /libstd/slfill.myr/
pkg std = generic slfill : (sl : @a[:], v : @a -> @a[:]) ;; generic slfill = {sl, v var i for i = 0; i < sl.len; i++ sl[i] = v ;; -> sl }