[plt-scheme] Compile error help

From: Tim Marchbank (tjm_22 at hotmail.com)
Date: Sun Nov 15 18:49:30 EST 2009

Hi,

 

Here is a simplified example of the problem I am having:

I open the following in DrScheme:

 

 

#lang scheme

(define (string-eval str) (eval (read (open-input-string str))))

(define (:Object-new c)
  (new (string-eval c))
  )

(define entity% (class object%
                   (field (Colour: "Red"))
                   (super-new)
                    )
  )

(define point% (class entity%
                  (field (X: 0.0))
                  (field (Y: 0.0))
                  (field (Z: 0.0))
                  (super-new)
                 )
   )

(define aa (:Object-new "point%"))
(define ab (:Object-new "entity%"))

 

 

When I run it, it comes up with the following error:

 

compile: unbound identifier (and no #%top syntax transformer is bound) in: point%

 

but then when I enter the last two lines into the interactions window, directly after the error, it works:

 

> (define aa (:Object-new "point%"))
(define ab (:Object-new "entity%"))
> aa
#(struct:object:point% ...)
> ab
#(struct:object:entity% ...)

 

Why does it work one time & not the other??

 

Any help would be appreciated.

 

Thanks

 

Tim.

 
 		 	   		  
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