**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)

![add 2 vectors](screenshot.png? "add 2 vectors")
  
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()```