The pictionary game

• How difficult it is to describe to someone how to draw something?
  • Instructions may be ambiguous
  • Different backgrounds, ways of interpreting…
• So happens with programming. The drama of programming is the drama of all human communication/expression…

Example: Drawing a rectangle

• Say to a computer “Draw a red rectangle in the top left corner of the screen.”

  • What shade of red, precisely?
  • How big should the rectangle be?
  • Exactly in the top left, or with some padding, and how much?
  • When should it be drawn?
  • What is the “top” of the screen on a mobile device that can be rotated?

• Code in Javascript:

// Get the canvas on the webpage that we want to render to.
let c = document.getElementById("myCanvas");
// Ask the canvas for an object that knows how to render 2-dimensional graphics onto the canvas.
let renderer = c.getContext("2d");
// Set the color to render, then draw a 100 x 100 pixel rectangle.
renderer.fillStyle = "rgb(255, 0, 0)";
renderer.fillRect(0, 0, 100, 100);

• Notice that many things that do not matter when we give instructions to other people actually do matter for the computer. And vice-versa…
  • Why is that?