PLT developers-
If I am developing a teachpack that is intended for use with the
Student languages (Beginning Student et al), how do I override how
structures I define are printed?
Searching the documentation for "constructor style printing" sent me
to the mzlib/pconvert library, and I figured out how to achieve this
when one is using the install-converting-printer procedure to turn on
constructor style printing. But then when I tried to require my
module as a teachpack into Student code, it continued to print using
the internal structure constructor name.
----
By the way, its really hard to understand the current mzlib/pconvert
documentation. But my current hypothesis is that I was wrong to try
to adapt that library for this goal anyway; it seems like it is
totally orthogonal to how the Student languages accomplish constructor
style printing. So perhaps the mzlib/pconvert library is deprecated
and the state of its documentation is irrelevant.
----
Example Code to illustrate what I am talking about:
;;; FILE: bug.ss
#lang scheme
(provide external)
(require mzlib/pconvert)
; (install-converting-printer)
(define-struct internal (value) #:transparent)
(define (external v) (make-internal v))
(current-print-convert-hook
(let ((old-hook (current-print-convert-hook)))
(lambda (v basic-convert sub-convert)
(if (internal? v)
`(external ,(sub-convert (internal-value v)))
(old-hook v basic-convert sub-convert)))))
;;; END OF FILE bug.ss
;;; FILE: bug2.ss
(require "bug.ss")
;; EXPRESSION DESIRED-OUTPUT ACTUAL-OUTPUT
(external 3) ; (external 3) (make-internal 3)
;;; END OF FILE bug2.ss
-Felix
_________________________________________________
For list-related administrative tasks:
http://list.cs.brown.edu/mailman/listinfo/plt-dev
