Re: [plt-scheme] define-structure question

[Matthew Flatt <mflatt@cs.utah.edu>]

At Wed, 12 Jun 2002 10:29:18 +1000, Chris Wright wrote:
> The help desk entry for define-structure isn't clear to me, and an example 
> would help.

Well, the documentation was wrong and the implementation was broken.
I've committed repairs to the CVS repository, including a patch to the
test-suite hole.

> (define-structure (name-identifier field ...))      SYNTAX

There should have been two cases:

  (define-structure (name-identifier field-identifier ...))

  (define-structure (name-identifier field-identifier ...)
                    ((init-field-identifier init-expr) ...))

In other words, fields with initialization expressions are declared
between a second set of parentheses.

Here's an example:

 > (define-structure (add left right) ([sum (+ left right)]))
 > (add-sum (make-add 3 6))
 9

but unless you're using CVS, that won't work until v200 is released.

Matthew