Function perpendicular

src/geode/geometry/perpendicular.cpp:30–33

namespace geode
{
    Vector2D perpendicular( const Vector2D& v )
    {
        return Vector2D{ { v.value( 1 ), -v.value( 0 ) } };
    }

    double dot_perpendicular( const Vector2D& v0, const Vector2D& v1 )
    {