[racket] inherit, inherit/super, and inherit/inner in class syntax

Dr./Mr./Ms. Takikawa, thank you for advancing my understanding.

I would still like to understand what inherit/inner is and how it works.  Can anyone else fill me in on this point?

--Christopher


On Jun 14, 2013, at 4:13 PM, Asumu Takikawa <asumu at ccs.neu.edu> wrote:

> On 2013-06-14 14:39:57 -0600, Christopher wrote:
>> So I have been trying to learn the ins and outs of Racket's class
>> system.  I've a little puzzled when it comes to the "inherit"-forms.
>> I've poured over the Racket Reference and fiddled with some
>> experimental classes, but I'm still not clear.
>> 
>> My questions specifically are, What is the difference between inherit
>> and inherit/super, and how does inherit/inner work?
> 
> Here's an example that hopefully shows the difference:
> 
>  #lang racket
> 
>  (define point%
>    (class object%
>      (inspect #f) ; to make example object easier to understand
>      (super-new)
>      (init-field [x 0] [y 0])
>      (define/public (move-x dx)
>        (new this% [x (+ x dx)] [y y]))))
> 
>  (define fast-point%
>    (class point%
>      (super-new)
>      (inherit/super move-x)
>      ;; or you can inherit
>      ;(inherit move-x)
>      (define/public (move-fast dx)
>        ;; only with inherit/super or override
>        (super move-x (* dx 10))
>        ;; with inherit, inherit/super, or override
>        ;(move-x (* dx 10))
>        )))
> 
>  (send (new fast-point% [x 0] [y 2]) move-fast 3)
> 
> Notice that with `inherit/super`, you can use `super` on the method name
> that you inherit from the superclass. Normally, you can only call
> `super` on a method name that you are overriding.
> 
> On the other hand, with either `inherit` or `inherit/super`, you can
> call the superclass method by just using the name.
> 
> I have never found the need to use `inherit/super` or `inherit/inner` in
> my programs though. I always use `inherit`.
> 
> (If you wanted to know the rationale of why `inherit/super` exists, I'm
> not sure. The commit log says it was added to replace `rename-super`
> eventually)
> 
> Cheers,
> Asumu