c++ - Sort vector based on value outside of class -

i have std::vector<mystruct>, simple version of struct this:

struct mystruct {     glm::vec3 position; }; 

the above struct declared in class:

class myclass {     private:         struct mystruct {             glm::vec3 position;         };      std::vector<mystruct> structvector;     glm::vec3 outsideposition;  }; 

but issue i'm having how sort structvector based on distance between structvector.position , outsideposition.

i've tried using std::sort this:

std::sort(this->structvector.begin(), this->structvector.end(), this->sortfunction); 

where sortfunction declared as:

glboolean myclass::sortfunction(mystruct const &x, mystruct const& y) {     glfloat dist1 = glm::length(this->outsideposition - x.position);     glfloat dist2 = glm::length(this->outsideposition - y.position);     return dist1 < dist2; } 

but compilation error stating there's no overloaded method std::sort. going wrong here?

errors:

error c2672 'std::sort': no matching overloaded function found

error c3867 'myclass::sortfunction': non-standard syntax; use '&' create pointer member

std::sort takes predicate compare element.
method requires information, have bind in way;
lambda (via capture) simple one:

std::sort(structvector.begin(),           structvector.end(),           [this](mystruct const &lhs, mystruct const& rhs)           {               return this->sortfunction(lhs, rhs);           });