alongLineAngleMoveDistancePt alongLineNormalDir alongLineNormalMoveDistancePt Angle Distance Distance FromPolar GetAngle IsEqual IsLess IsNull Length moveAlongLine Negate Normalize operator* operator* operator*= operator+ operator+ operator+= operator- operator- operator-= operator/ operator/= operator= operator== Perpendicular perpendicularPointOnLine ProjectToLine Rotate Scale Set Sqr Vector2d Vector2d Vector2d Vector2d x y

Sqr() double Sqr ( ) const 计算向量的平方长度 计算向量的平方长度，避免开方运算。 返回 向量的平方长度