<html> <head> <style></style> </head> <body class='hmmessage'>   Thanks for replying.   The reason I am doing it this way, is because it is the only way I could find to convert a string of a class into an input for new / make-object etc. (Probably comes back to the way I would have done it or something similar in VisualLISP.) Why do I want to do that? Well, I was wanting a common way of creating any class of object by passing its class (and other initialisation variables) to a common function, and sending it as a string seemed the most useful means (as I can then use it dialogs etc..) As I said, this is only a simplified version of what I am working on.   If there is a better way to do it, I'm all ears.   But.. Why does it not work, and then work?   Still learning..   Tim.   > Date: Sun, 15 Nov 2009 17:08:48 -0700 > From: czhu@cs.utah.edu > To: tjm_22@hotmail.com > CC: plt-scheme@list.cs.brown.edu > Subject: Re: [plt-scheme] Compile error help > > Could I ask why you use `eval' here? The error is related to the way you > use `eval'. Most of the time, people misuse `eval' (i.e., use eval when > they shouldn't). > > Chongkai > > Tim Marchbank wrote: > > 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. > > > > > > ------------------------------------------------------------------------ > > With all the lastest places, searching has never been easier. Look > > now! Looking to move this spring? > > <http://clk.atdmt.com/NMN/go/157631292/direct/01/> > > ------------------------------------------------------------------------ > > > > _________________________________________________ > > For list-related administrative tasks: > > http://list.cs.brown.edu/mailman/listinfo/plt-scheme > > > <hr />Check out The Great Australian Pay Check now <a href='http://clk.atdmt.com/NMN/go/157639755/direct/01/' target='_new'>Want to know what your boss is paid?</a></body> </html>