帮忙看下，为什么提示我函数没有定义。

#include <iostream>
#include <string>
#include <iomanip>
#include <fstream>
#define TURE 1;
#define ERORR 0;
#define OK 1;
#define FALSE 0;
using namespace std;
class city
{                                           //      用类定义城市坐标
public:
    char name;
    float x;                                                 //         经度
    float y;                                               //      纬度

    class city *next;
    void inset(city *p);
    void set(char n,float a,float b)
    {
        name=n;
        x=a;
        y=b;
    }
};
void city::inset(city *p)
{
    ofstream outfile("date.txt",ios::out);
        if(!outfile)
        {
            cout<<"error"<<endl;
            exit(1);
        }
    while(p->next!=NULL)
    {
        cout<<p->name<<"  "<<p->x<<"  "<<p->y;
        outfile<<p->name<<"  "<<p->x<<"  "<<p->y;
    }
    outfile.close();
}

int main()
{
    char name;
    city c1,c2,c3;
    city *head,*p,*q;
    q=head=new city;
    for(int i=0;i<3;i++)
    {
        p=new city;
        cout<<"name";
        cin>>p->name;
        cout<<"a";
        cin>>p->x;
        cout<<"b";
        cin>>p->y;
        q->next=p;
        q=q->next;
    }
    inset(head);
    return 0;
   
}