Hi, In message "Re: Subrange of String subclass => invalid object" on 02/01/30, Mathieu Bouchard <matju / sympatico.ca> writes: |Object#become is not an essential feature, but the same can be said of |#callcc and retry... somewhere a line has to be drawn. the question is |"where?"... It's both easy and hard question. Easy answer is, as Hal Fulton quoted in his book: "follow your heart". Hard answer is .. well .. it's too hard to say. ;-) matz.