code: function transform (observable, down, up) {
    return function (val) {
      return (
        get(val) ? down(observable())
      : set(val) ? observable((up || down)(val))
      : observable(function (_val) { val(down(_val)) })
      )}}
docs: ^ if written in this style, always ends )}} /*
  note the use of the elvis operator `?:` in chained else-if formation,
  and also the comma operator `,` which evaluates each part and then
  returns the last value.
  
  only 8 lines! that isn't much for what this baby can do!