Did you find define-local-member-name? Robby
On Wed, May 11, 2011 at 7:32 PM, Mark Engelberg <[email protected]> wrote: > On Wed, May 11, 2011 at 1:10 PM, David Van Horn <[email protected]> wrote: >> Here are some struct definitions and a function, based on Land of Lisp: >> >> (struct monster (id [hit #:mutable]) #:transparent) >> (struct orc monster (club) #:transparent) >> (struct hydra monster () #:transparent) >> (struct slime monster (sliminess) #:transparent) >> (struct brigand monster () #:transparent) >> >> (define (damage! m n) >> (set-monster-hit! m (max 0 (- (monster-hit m) n)))) > > I'd like to be proven wrong, but I really think you have to use OO > techniques to achieve this kind of polymorphism in Racket. > > I wrote Land of Lisp's orc battle in a few different ways, exploring > stylistic variations using Racket's class system, which I had never > used before. In one version, I made all the "fields" private, e.g., > with (define agility 30), and then explicitly made getter and setter > methods. In another version, I specifically used the field construct, > e.g., (field [agility 30]) so I wouldn't have to write the getter and > setter methods. > > I wasn't entirely happy with either version. I felt that the code > would have been much cleaner if there were some sort of analog to > "protected" fields and methods, in which the subclasses could see the > fields and methods but outside classes could not. The > private-with-accessors version was rather verbose. On the other hand, > when working up the field version, I felt the code was somewhat > klunky; I was frequently tripped up by the fact that field accessors > place the field name first and object second, whereas send places the > object first and the method second. Furthermore, fields have their > own verbosity -- overriding the initialization of a field in a > subclass is a two-step process, for example, and you end up with a lot > of inherit-field statements if you want to access fields in a manner > that's consistent with new fields. > > Ultimately, I decided that the field version was the cleaner of the > two, but I remain interested in seeing if there is a better way to > code it using Racket's constructs. > > If you're curious, I can send you my code samples off-list. > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
