code: function(v) {
              	if (typeof(v) == 'number')
              	    return this.map(function(k) { return k - v; });
  
              	var V = v.elements || v;
              	if (this.elements.length != V.length) { return null; }
              	return this.map(function(x, i) { return x - V[i - 1]; });
                  }
docs: Returns the result of subtracting the argument from the vector