MatRepl

• is a Matrix
• and a repl: Read–Eval–Print Loop, where Print is doing operations on vectors and matrices in a graphic environment
• written in vanilla javascript (ES6)

The repl has the following syntax (It's work in progress, new capabilities will be added)

• arithmetic expressions:
  • add, subtract, divide, multiply
• variable declaration eg: a= ... vector(1,2,3,4) adds a vector, vector(1 2) as well. The start is now the origin. commas are not mandatory. I'm planning to add a more mathematical notation for vectors: [1 2]

  • > vector@0{x0:1, y0: 2, x:3, y:4}

• remove(x) removes bindings (when it's an object (eg vector), removes it from the matrix)
• remove(@n) removes an object using it's assigned index (n is a number)
• method calls: a = vector(12,1)

  > vector@0{x0:1, y0: 2, x:12, y:1}

• properties
• a.type

  > vector

• property lookup a.x+1

  > 13

• drag vectors using the mouse pointer. You can change the vector arrows visually
• lazy evaluation. The difference between c = a+b and c = "a+b" is that the latter assigns to c a parsed expression that can always be evaluated later. When you apply lazy evaluation and later update a, the value for c will be reevaluated automatically. Combined with vector dragging, this way you can get an intuition for vector addition. Want to do the same for matrix multiplication and basis change.
• enter the following:

  a = vector(0.5, 0.5)
  b = vector(-1, 1)
  c = "a+b"
  

• and press enter. Then using the mouse pointer move a or b. Or try: a=2*a This updates vector a to twice it's size. And, because c is defined lazily, it is updated as well!

To run locally

• make sure you have node/npm
• cmdline: npm run start
• and enter help()