code: function(matrix) {
              	var M = matrix.elements || matrix;
              	if (typeof(M[0][0]) == 'undefined') { M = Matrix$b.create(M).elements; }
              	// this.columns should equal matrix.rows
              	return (this.elements[0].length == M.length);
                  }
docs: Returns true iff the matrix can multiply the argument from the left