Plotting in a Racket Notebook

:: programming, racket

I recently started experimenting with the Racket notebook package, IRacket. Notebooks are handy for experimentation and visualization, so I wanted to be able to display a plot. I discovered that (require plot) did not work, but if I changed that slightly to (require plot/pict), I was able to display a plot in the notebook.

This is an example of plotting in a notebook from Advent of Code 2021 - Day 17:

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#lang iracket/lang #:require racket

(require plot/pict)

(define-values (x-max y-min) (values 250 -105))

(define (trajectory dx dy [x 0] [y 0] [ result '() ])
  (if (or (> x x-max) (< y y-min))
      (reverse result)
      (let ([ result (cons (list x y) result) ]
            [ dx (cond [ (> dx 0) (sub1 dx) ]
                       [ else     dx        ]) ]
            [ dy  (sub1 dy)   ]
            [ x   (+ x dx)    ]
            [ y   (+ y dy)    ])
        (trajectory dx dy x y result))))

(define (plot-trajectory dx dy)
  (let ([ pts (trajectory dx dy) ])
    (plot (list (rectangles (list (vector (ivl 206 250) (ivl -57 -105))))
                (points pts))
          #:x-min -1
          #:x-max 300
          #:y-min -150
          #:y-max 200)))

(plot-trajectory 21 12)