[plt-scheme] viewport graphics problem

From: James E. Hoburg (hoburg at acm.org)
Date: Thu Jul 8 14:38:02 EDT 2004

When I use the viewport graphics features like so:

     (require (lib "graphics.ss" "graphics"))

     (define w (open-viewport "test" 16 16))

     ((draw-pixel w) (make-posn 7 7))
     ((clear-pixel w) (make-posn 7 7))

I get this error:

     Welcome to DrScheme, version 207.
     Language: Pretty Big (includes MrEd and Advanced).

     . procedure clear-pixel-viewport: expects 2 arguments, given 1: 

In short, I can't seem to get clear-pixel to work as documented.  What 
am I doing wrong?


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