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Re: Problems with field initialization

This page is part of the web mail archives of SRFI 76 from before July 7th, 2015. The new archives for SRFI 76 contain all messages, not just those from before July 7th, 2015.

On Wed, 14 Sep 2005, Andre van Tonder wrote:

Alternative Suggestion:

Instead of having a separate <init expression> for each field, one could
simply have an <expression> for the constructor, which should evaluate to a
procedure that returns the computed fields (using VALUES, for example).

This would solve all the above problems.  The overall gain in power and
simplicity would be, in my view, significant.

By the way, it has occurred to me that, if one were to consider the functionality of INIT! to be justified, even INIT! may be dropped if the user-provided constructor procedure is specified abstracted over the "real" constructor.

For example:

(define *the-frob* #f)

(define-type frob (lambda (real-constructor)
                    (lambda (n)
                      (let ((result (real-constructor (make-widget n))))
                        (set! *the-frob* result)
  (fields (widget (getwid setwid!))))