Yikes! Spent quite a few hours yesterday wrestling with a DynamicModule problem (or at least I thought it was) before writing it up to ask the experts at mathematica.stackexchange.com. Whereupon I was almost immediately informed that a particular ; should have been a , and that was my entire problem.

Syntax counts! Even just a single dot! Code carefully!

(And of course this error has a lot to do with years of programming in languages that use ; as a separator or statement terminator, which is not the Wolfram Language way ...)

(BTW Evaluation > Analyze Notebook seems useful but didn't catch this error.)

That "Updating Name" = me. :)

An EventHandler[] toy: 25 particles (circles) interact with each other. They eventually settle down into some sort of flow, with the occasional random circle deciding they like someone else. Click and drag to move one and upset the status quo.

DynamicModule[{
  n = 25, (* number of pts (constant) *)
  pts,
  drag = {} (* index of pt being dragged *)
  },
 pts = RandomReal[{-1, 1} 25/Sqrt[3 n], {n, 2}];
 EventHandler[
  Deploy@Graphics[ (* Deploy[] turns off the usual Graphics interactions *)
    Dynamic@GraphicsComplex[ (* efficient way to manage a figure that is a function of points *)
      pts = (* move[] the points, except the one being dragged *)
       ReplacePart[pts + move[pts], # :> MousePosition["Graphics"] & /@ drag],
      {Hue[#/n], Sphere[#, 0.7/Sqrt[n]]} & /@ Range[n]],
    PlotRange -> 25/Sqrt[n]
    ],
  (* mouse up/down: de/register which point is to be dragged *)
  {"MouseDown" :> (drag = Nearest[pts -> Automatic, MousePosition["Graphics"]]),
   "MouseUp" :> (drag = {})}
  ],
 Initialization :> ( (* define how the points move *)
   ClearAll[move];
   (* it returns changes in position for each point in the list p *)
   move[p_List] := Module[{$n, interaction},
     $n = Length[p];
     interaction = Array[
         Function[{row, col},
          Exp[-Abs[(row - col)/4] + 0.5 UnitStep[row - col] - 0.25]]
         , {$n, $n}
         ]/(IdentityMatrix[n] + DistanceMatrix[p])^2 // Function[mat,
        DiagonalMatrix[Total[mat] - 0.01 $n] - mat];
     0.2*(interaction . p)
     ];)
 ]

I would have posted a cloud notebook, but it didn't render. Maybe Dynamic[] doesn't work so well there?

Rory said carte blanche today that his Pacman-like video game will not run off of the cloud. If you looked at my cloud code showing Rope Flow under a monolith, the animation is quite squirrelly. The 3D cursor won't change the perspective of the frame until you PAUSE the moving ball.

I am looking at using CDF (Computable Document Format) for deploying some code. It runs against the Wolfram Player, which is basically a read-only version of the Wolfram Language. Wolfram has de-emphasized this approach over the last few years, but it's still viable. Apparently, users balked at downloading the multi-GB Wolfram Player.

Claude has some suggestions on how to make Dynamic viable. You can just put your whole block of code in and have Claude stick in its suggestions. Their code generation is much improved from 6 months ago.

This is a super little interactive example.

I don't think the staff want to talk about particular quiz answers. For what it's worth, I also tend to think there's something wonky about that question. OTOH, there is value in deeply understanding the difference between == and ===; that's the real point of the question.

You reminded me of one nice feature of the Wolfram Documentation. You can enter any function shortcut into the search panel at the top of the documentation (e.g., ===, @@@, @, etc.) and the documentation will give you the Full Form of that function shortcut and go to the appropriate documentation page.

If you have Wolfram Language installed in your local machine, it's incredibly useful to have the documentation also installed. Each page in the documentation is a full live Wolfram Language Notebook, and you're more than welcome to start actively evaluating expressions in the middle of any documentation page. There's something deeply Stephen Wolfram about that; I could imagine him doing that when he's typing in Notebooks for hours every day. It almost feels like cheating.

I've never seen tabbed notebooks, but Documentation`HelpLookup[""] or Documentation`HelpLookup["SameQ"] will bring up a new, additional help notebook.

I've sometimes opened two help browsers by accident, too, just doing ordinary cmd-F or menu actions. I don't why it sometimes does that. It doesn't happen often. It may have been a bug in a particular version.

Post on "The King's Speech" was mine - for some reason the forum didn't attribute it to me.

We hear you. Good things are coming up!

I extended the project a bit and replaced everything. Well, except "the" since the entity type "Determiner" had a random (grammatical) number, and I could not determine the number in WL; and "to", which is an infinitive marker, not a preposition. Another problem is than RandomWord[type] sometimes comes up with words that cannot be of the type, except in the sense that in English most words can be used metaphorically as most parts of speech. And sometimes in the cloud, the random word generation is too slow for the time limits in the cloud. Of course, random words generate nonsense, but sometimes it's fun.

Inspired by class today...

A couple of things:

• The image data has three numbers in a list {r, g, b} that represent a color. RGBColor @@ {r, g, b} yields the color RGBColor[r, g, b].
• It turns out that the position of a color datum in the data is flipped from the usual graphics coordinates: Horizontal and vertical positions are switched, and the vertical position increase from top to bottom instead of from the bottom up. That's the reason for the odd matrix multiplication ({{0, 1},{-1, 0}}).position.

The code layers dots on top of each other, decreasing in radius from maxRadius pixels down to 1 pixel. The color for each dot corresponds to the color of the pixel in the image at the center of the dot. Layering the smaller dots on top allows the resolution to improve. Lots of things to play with: how the radii change, how large the disks, how many disks — all affect the texture, identifiability. You can play with the color space to get a reddish tiger by replacing Extract[data, position]] with Clip[RotationMatrix[-Pi/3, {1,1,1}].Extract[data, position]].

I've been doing Rope Flow for about 10 years. It's a means of moving laterally with a jump rope without jumping over the rope. Here is a sample of the Rope Flow "Dragon Roll" from an instruction video on YouTube. I'm marking the middle and endpoints of my rope with distinct bright colors and will make a short slow-motion video of the "Dragon Roll" this weekend. I'll use the Wolfram Language's simple motion-tracking capability and try to plot the rope's motion in 3D. Next, I'll see if the WL can identify the 3D curve of the "Dragon Roll". Based on the figure-eight (i.e., lemniscate) shadow of the path, I've got a pretty good guess what the path might be. That Mathworld entry even mentions my guess. We shall see. :)

This is a marvelous STEM application. Students learn about sine waves in geometry and more advanced HS math classes. The "Dragon Roll" allows them to stand under and make sinusoidal waves -- front-back, left-right, and up-down -- all at the same time.

You can see the component sine waves by orienting this Wolfram 3D graphic to various sides. The monolith is in the center to represent how the rope criss-crosses over the flow-roper. Note: you can only change the 3D orientation if the animation is not playing. I apologize for the janky animation of the red ball. I need to figure out how to make it smoother when running off of a cloud computer. You can download the Notebook or just copy the expression into your local version of Mathematica.

If this works, I may reach out to a couple of the Rope Flow schools to show them the idea. I'm looking forward to [reviewing] Rory's Creative Computation class next week.