ref: a277cea8fabeb3ec38484ffc461ae86e5fd8f9b5 dir: /lib/std/slfill.myr/
pkg std = generic slfill : (sl : @a[:], v : @a -> @a[:]) ;; generic slfill = {sl, v for var i = 0; i < sl.len; i++ sl[i] = v ;; -> sl }