Yes, this does exactly what I expected the original to do. Thanks!

John

> On Jul 31, 2019, at 23:11, Gregory Cooper <[email protected]> wrote:
> 
> Hi John,
> 
> It's been several years since I've looked at this, but what happens if you 
> change the require line to:
> 
> (require (lifted (only-in 2htdp/image square) square))
> 
> (and, I guess, update the constant that you're subtracting from `seconds`)?
> 
> --Greg
> 
> 
> On Tue, Jul 30, 2019 at 11:43 AM 'John Clements' via dev-redirect 
> <[email protected]> wrote:
> I was messing around with Father Time today and wrote this program:
> 
> (require 2htdp/image)
> 
> (square 
>  (- seconds 1564512004)
>  "solid"
>  "blue”)
> 
> I expected to see a growing blue square, but instead got:
> 
> .../lang/prim.rkt:24:44: square: expects a non negative real number as first 
> argument, given (signal 145 '() #f #<procedure:...ime/lang-ext.rkt:646:20> 2 
> #<continuation-mark-set> #<parameterization> (list (signal 1564512149 
> '(#<weak-box>) #f #<procedure:...ime/lang-ext.rkt:467:23> 1 
> #<continuation-mark-set> #<parameterization> '()) 156451…
> 
> Somehow the “I’m a signal but I’m also a number” abstraction didn’t quite 
> flow through the “square” primitive. Is this supposed to work?
> 
> John
> 
> 
> 
> 
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