Tests your functions. Use Rackunit Luke. On Aug 11, 2013, at 3:40 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 <matth...@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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