On Sun, Jan 20, 2013 at 6:25 PM, Matthias Felleisen <[email protected]> wrote: > > Normal OOPLs suffer from a lack of expressiveness. > OO programmers make up for this lack with programming > patterns. If you don't have first-class functions, > simulate them with the command pattern. If you don't > have functions but you want to emphasize functional > style, use the visitor pattern. > > The extensible visitor pattern is the only contribution > in the book that is of some interest to Racket programmers. > But we have units and mixins, and we can do this thing > even better. > > Once we have types for these, the question becomes whether > the type system will be strong enough to get away without > the one ugly cast. > Many thanks Matthias.
1) What I found useful in the book is the way it shows recursion with OOP, I had never seen this before. About the recursion in the book. The examples so far all depend on the last object in the recursion being a particular class to end the recursion. For example to use the shish-kabob example, I can construct the following two shish-kabob but only the first gives the correct answer because the recursion ends in skewer%, Example 1: gives correct answer (define shish-c (new onion% [sh (new onion% [sh (new lamb% [sh (new skewer%)])])])) (send shish-c only-onions? ) Example 2: gives incorrect answer (define shish-c (new onion% [sh (new onion% [sh (new skewer% [sh (new lamb%)])])])) (send shish-c only-onions? ) Is it possible to make a contract that will flag example 2 as a contract violation? 2) Regarding types, I see that "The Little MLer" is about types. Would it be useful for a Racket programmer who only knows C types, to go through "the little MLer" but using typed Racket instead of ML. Thanks, Harry Spier ____________________ Racket Users list: http://lists.racket-lang.org/users
