丢弃限定符 -允许

嗨，伙计们，我犯了一个错误，我无法在void GPSPathList上 understand.in 我的主要类：:p rint(( const我收到此错误。

[Error] passing 'const GPSPathList' as 'this' argument of 'void GPSPathList::print_item(const GPSPathList::GPSCoordNode*)' discards qualifiers [-fpermissive]

你能帮忙吗

我的标题

#ifndef GPSPATHLIST_H
#define GPSPATHLIST_H
class GPSPathList {
     public:
        GPSPathList(){ m_size = 0; m_item_list = 0; }
         int size() const{return m_size;}
    void add_from_user();
    void print() const;
    double total_distance();
    private:
        struct GPSCoordNode{
            double longtitude;
            double lattitude;
            GPSCoordNode *next;
        };
    void print_item(const GPSCoordNode *item);
    void addpoint(const double& lattitude, const double& longtitude);
     int m_size;
    GPSCoordNode *m_item_list;

};
#endif

我的主要

#include "gpspathlist.h"
#include <iostream>
#include <cmath>
using std::ifstream;
using std::cout;
using std::cin;
using std::endl;
using std::string;
void GPSPathList::print_item(const GPSCoordNode *item){
cout<< "<"<<item->lattitude<<","<<item->longtitude<<">"<<endl;
}
void GPSPathList::addpoint(const double& lattitude , const double& longtitude){
     GPSCoordNode *new_point = new GPSCoordNode;
        new_point->lattitude = lattitude;
        new_point->longtitude = longtitude;
        if (m_item_list == 0 ) {
                new_point->next = m_item_list;
                m_item_list = new_point;
                    } 
                    else {
                GPSCoordNode *p = m_item_list;
                while (p->next != 0)
                        p = p->next;
                new_point->next = p->next;
                p->next = new_point;
        }
        m_size++;
}
void GPSPathList::add_from_user(){
string a;
double lattitude,longtitude;
    while(true){

    cout << "Enter lattıtude : " <<endl;
                cin >> lattitude;
                cout << "Enter longtıtude : " <<endl;
                cin >> longtitude;
                 addpoint(lattitude,longtitude) ;
                    cout <<"if exit press no to ";               
                 cin >>a;
                 if(a=="no"){
                    break;
                 }
                 }
                 }
void GPSPathList::print() const
{
        const GPSCoordNode *d = m_item_list;
        while (d != 0) {
                print_item(d);//my problem is in here
                d=d->next;

        }
}
double GPSPathList::total_distance(){
double a,b,c,d,longtitude,lattitude,longtitude2,lattitude2,R,S;
 GPSCoordNode *v = m_item_list;
  for (int i =0; i<m_size; i++){
    a=v->lattitude;
    b=v->longtitude;
    v=v->next;
      c=v->lattitude;
      d=v->longtitude;
        v=v->next;
      i++;
         R = 6371.8; 
    longtitude= (3.141593/180.0) * b;
    lattitude = (3.141593/180.0) * a;
    longtitude2=(3.141593/180.0) * d;
    lattitude2=(3.141593/180.0) * c;
    double  Lat =lattitude2-lattitude;
   double   Lon = longtitude2-longtitude;

    double w = sin(Lat / 2); 
    double x=sin(Lon / 2); 
     double q= R * asin(sqrt((w*w)+(cos(lattitude) * cos(lattitude2)*x*x)));

i++;  
return S=q*1.609;
 cout<<" distance: "<< S;
 }
}
int main(int argc, char** argv){
GPSPathList a;
 a.add_from_user();
 a.print();
 a.size();
 a.total_distance();

}

嗨，伙计们，我犯了一个错误，我无法在void GPSPathList上 understand.in 我的主要类：:p rint(( const我收到此错误。