Re: readable interfaces with pint

[mike@olan.com (Michael N. Livshin)]

Klaus Schilling <Klaus.Schilling@home.ivm.de> writes:

> Are there any working examples out there how to define read and write-syntaxes
> for interfaces defined with pint?

I think I've understood you right, so here goes:

<REPL>

guile> (define-module (rw-test) #:use-module (oo interface))
#<directory rw-test 401c0980>
guile> (define-interface-type <rw-number>
          "readable and writable number"
          ;; inherits from these two guys:
          (<readable> <writable>)
          ;; no constructors:
          ()
          ;; one new method:
          (invert!))
guile> (define-interface-mapping plain-number-mapping
          "rw for plain numbers"
          <rw-number>
          ;; here, only invert! is defined,
          ;; because the default implementations of
          ;; make/port & write are just fine.
          #:invert! (lambda (interface)
                      (set-interface-data! interface (- 0
                                                     (interface-data interface)))))
;; read a number from port:
guile> (define num (make-interface/port plain-number-mapping))
;; this is the input:
123
;; now check what we've just read:
guile> num
#<interface (#<mapping "rw for plain numbers" (type: "readable and writable number")> data: 123)>
;; invert it:
guile> (rw-number-invert! num)
;; write it back:
guile> (write-interface num)
-123

</REPL>

Now, I think what really confused you is that the current version of PINT has
bugs in the definitions of <readable> and <writable>, so the above doesn't work :(.

That's what you get when you don't test everything...

I'm uploading the fixed version right now, snarf it when it gets out of the
incoming directory.

> Klaus Schilling

Nice to know that somebody is actually trying to use this stuff.

mike.