src/Maths/Algebra/Matrix.php
public function previous()
    {
        if ($this->getWalkFlag() & self::WALK_X) {
            return $this->previousX();
        } elseif ($this->getWalkFlag() & self::WALK_Y) {
            return $this->previousY();
        } else {
            return $this->previousXY();
        }
    }
public function previous()
    {
        if ($this->getWalkFlag() & self::WALK_X) {
            return $this->previousX();
        } elseif ($this->getWalkFlag() & self::WALK_Y) {
            return $this->previousY();
        } else {
            return $this->previousXY();
        }
    }
Go to previous index according to matrix's flag value

@return  $this
@see     self::previousX()
@see     self::previousY()
@see     self::previousXY()