[racket-dev] relationship between define-struct and struct

The student languages have a completely separate implementation of
define-struct from Racket.

[lang/private/teach.rkt: do-define-struct: line 716

For a reason unknown to me, the struct type descriptor [line 805]
returned by make-struct-type does not get defined (although it does
check to make sure it could be defined.) [line 931]

I'm not entirely sure why this is although I anticipate that is has to
do with the fact that such a value has no worth in *SL, because there
are no operations on it. Thus it would be very awkward in the docs to
say that a thing is defined with define-struct that has no meaning to
students.

Since struct-out expects this thing to be defined, it errors. It is a
bit awkward that the error suggests that it should have been imported,
rather than defined in the file.

Jay

On Sat, Aug 28, 2010 at 1:23 PM, Shriram Krishnamurthi <sk at cs.brown.edu> wrote:
> What is the relationship between define-struct and struct in Racket
> 5.0.1?  By define-struct I mean the construct provided in ASL.  In my
> custom language I have
>
> (define-struct tv (tag value))
> (provide (struct-out tv))
>
> and I get the error
>
> struct-out: no import for structure-type identifier in: struct:tv
>
> Is this because define-struct suppresses the struct:tv "structure-type
> information"?  (If so, why?)  ((And if so, is there a way to make
> struct-out work shy of copying the implementation of define-struct and
> adding/removing the line that hides this?))
>
> Shriram
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-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://teammccarthy.org/jay

"The glory of God is Intelligence" - D&C 93