[racket] use plot as render in universe

Sorry I'm late. :D

You can make your plots more robust to "can't determine bounds" errors 
by including an `invisible-rect' or `invisible-rect3d' renderer in the 
plot, with fully specified (i.e. non-#f) bounds. The plots' bounds will 
always include the invisible rectangle.

Another option is to explicitly pass #:x-min, #:x-max, etc. keyword 
arguments to `plot'. Any bounds you set that way will be fixed.

Do you mind if I ask what you're up to?

Neil ⊥

On 08/11/2013 01:40 PM, J G Cho wrote:
> Thanks for the assurance. It helped me to focus on my
> world->list-of-vectors It turns out it did not return enough vectors (at
> least 2, I think) for initial-world.
>
>
>
>
> On Sun, Aug 11, 2013 at 12:34 PM, Matthias Felleisen
> <matthias at ccs.neu.edu <mailto:matthias at ccs.neu.edu>> wrote:
>
>
>     On Aug 10, 2013, at 7:04 PM, J G Cho wrote:
>
>>     I get an error (somewhat expectedly) when I try
>>
>>       (big-bang init
>>                 (on-tick random-walk 1)
>>                 ;(on-key door-actions)
>>                 (to-draw plot-render)
>>                 ))
>>
>>     where plot-render is defined as
>>
>>     (define (plot-render world)
>>       (p:plot (p:lines
>>              (world->list-of-vectors world)
>>              #:color 6 #:label "Random walk")))
>>
>>     with the following at the top
>>
>>     (require (prefix-in p: plot))
>>
>>     The error msg is
>>
>>     plot: could not determine sensible plot bounds; got x ∈ [0,0], y ∈
>>     [1,1]
>>
>>     Is there way to let plot know of the context? Or pass a context to
>>     plot and extract the pixels and hand it over to via some proc in
>>     2htdp/image? Or maybe there is a simple way?
>
>
>     This works like a charm for me:
>
>     #lang racket
>
>     (require (prefix-in p: plot) 2htdp/universe)
>
>     (define (plot-render world)
>        (p:plot (p:lines (world->list-of-vectors world)
>                 #:color 6 #:label "Random walk")))
>
>     (define (world->list-of-vectors world)
>        `(#(1 3) #(2 -2) #(4 3)))
>
>     (define (random-walk world)
>        'more-dummy)
>
>     (big-bang 'dummy ; init
>                (on-tick random-walk 1)
>                (to-draw plot-render))
>
>     ;; ---
>
>     When I had a student implement the first plot version, I
>     intentionally made sure that plot returned something I could use in
>     big-bang.
>
>     And btw, this works too:
>
>     #lang racket
>
>     (require (prefix-in p: plot) 2htdp/universe 2htdp/image)
>
>     (define (plot-render world)
>        (overlay
>         (p:plot (p:lines (world->list-of-vectors world)
>                          #:color 6 #:label "Random walk"))
>         (square 800 'solid 'blue)))
>
>     (define (world->list-of-vectors world)
>        `(#(1 3) #(2 -2) #(4 3)))
>
>     (define (random-walk world)
>        'more-dummy)
>
>     (big-bang 'dummy ; init
>                (on-tick random-walk 1)
>                (to-draw plot-render))
>
>
>
>
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