code: function UpInputs(elt, upwardable, realtime = false) {
    console.assert(elt instanceof HTMLInputElement, "First argument to UpInputs must be input element");
    console.assert(isUpwardable(upwardable), "Second argument to UpInputs (.inputs) must be upwardable");
  
    function observeUpwardable() {
      observe(upwardable, changes => changes.forEach(
        change => elt.value = change.newValue), ['upward']);
    }
  
    elt.addEventListener(realtime ? 'input' : 'change', _ => {
      upwardable = upwardable.change(elt.value);
      observeUpwardable();
    });
  
    elt.value = upwardable;
    observeUpwardable();
    return elt;
  }
docs: ## UpInputs (.sets)
  
  Associates an upwardable with the value of an input element.
  
  @param {HTMLInputElement} elt element to associate
  @param {Upwardable} upwardable upwardable to associate
  @param [boolean=false] realtime if true, update upwardable each char