symmetricmatrix.txt

Explanations for https://eloquentjavascript.net/06_object.html#c_uuBcsDdS7D

Matrix constructor:
this.content[y * width + x] = element(x, y);
-> this.content[3 * 5 + 2] = element(2, 3);

so, what is element(2,3)? element is the argument passed to the constructor, here (in symmetricMatrix):
super(size, size, (x, y) => {
      if (x < y) return element(y, x);
      else return element(x, y);
    });
    
-> So 'element(2,3)' in the Matrix class is:
  if (2 < 3) return element(3, 2); else return element(2,3);
-> Since 2 is smaller than 3, this simplifies to:
    return element(3, 2) 
    Where element is now the function you have passed into the SymmetricMatrix constructor, which is (x, y) => `${x},${y}`)
-> So element(3,2) is:
   `${3},${2}`
   That's why content[3 * 5 + 2] = '3,2' ;)