docs: function create2x2(a, b, c, d){
      if (undef(a)) throw new Error("At least one argument must be provided.");
  
      if (undef(b)){
          // Everything = a
          b = a;
          c = a;
          d = a;
      }
      else{
          // we have a and b
          if(undef(c)){
              c = a;
              d = b;
          }
          else{
              if(undef(d)) throw new Error("Argument 'd' must be provided if 'c' is.");
          }
      }
  
      return new Vector([[a, b],[c, d]]);
  }