[plt-scheme] how to creating a new "primitve type"

> You can do it in Scheme: define "ssn" as a structure in PLT Scheme, and 
> then use Readtable (chapter 11.2.8 of MzScheme) and the built-in 
> prop:custom-write structure type property to do read/write.

To make "equal?" work is a little tricky. Normally you will need to 
re-define "equal?":

(define (my-equal? p1 p2)
  (if (and (ssn? p1)
           (ssn? p2))
      ;your code to tell whether two ssn equal?
      (equal? p1 p2)))

If you use modules, than you can creat your own language as a extension of 
MzScheme: export "my-equal?" as "equal?", and everything else from MzScheme.

> Chongkai
>
> ----- Original Message ----- 
> From: YC
> To: mzscheme Mailing List
> Sent: Tuesday, May 08, 2007 1:44 PM
> Subject: [plt-scheme] how to creating a new "primitve type"
>
>
> Hi all -
>
> say that I want to create a new primitive type (something like path or 
> string) so it has the first class status (for the lack of a better term) 
> as the other primitive types.  How is this done, and Is this doable only 
> in scheme or does it involve working on C code?
>
> Example - social security number.
>
>> (define s1 #ssn"123-45-6789")
>> s1
> #ssn"123-45-6789"
>> (ssn->string s1)
> "123-45-6789"
>> (ssn? s1)
> #t
>> (equal? s1 #ssn"123-45-6789")
> #t
>> (equal? s1 #ssn"987-65-4321")
> #f
>
> Any pointer is appreciated ;)  Thanks,
> yinso
>
>
>
>
>
> _________________________________________________
>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> _________________________________________________
>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>