chickadee » random-access-lists » ral-map

function (result)
requires (and (ral? ls) (procedure? fn) "(fn item)"
              (procedure? item?) "(item? item)")
         ; default (eq? item? ral-item?)
ensures  (and (ral? result) (fx= (ral-count result) (ral-count ls))
              (eq? item? (ral-item? result)))