anchor.diff:     * Returns true if every elements of this collection satisify the
      * predicate [f]. Returns false otherwise.
      */
  -  bool every(bool f(T element)) {
  +  bool every(Func1<T, bool> f) {
       requireArgumentNotNull(f, 'f');
       for (final e in this) {
         if(!f(e)) {
  
positive.code:    * Returns true if one element of this collection satisfies the
     * predicate [f]. Returns false otherwise.
     */
    bool some(bool f(T element)) {
      requireArgumentNotNull(f, 'f');
      for (final e in this) {
        if(f(e)) {
  
negative.code:     return false;
    }
  
    Enumerable select(Func1<T, Object> f) {
      requireArgumentNotNull(f, 'f');
      return new _FuncEnumerable(this, (s) => new _SelectIterator(s, f));
    }
  