undefined reference to `setgolf(golf&, char*, int)'
collect2: error: ld returned 1 exit status

#ifndef SANS_H_INCLUDED
#define SANS_H_INCLUDED
const int len = 40;
struct golf
{
    char fullname[len];
    int handicap;
};

//void setgolf(golf &,char * ,int);
int setgolf(golf &);
void sethandicap(golf &,int );
void showgolf(const golf &);
#endif

#include <iostream>
#include <cstring>
#include "chapter9exe3.h"
void setgolf(golf & s,char *c ,int hc)
{
    strcpy(s.fullname,c);
    s.handicap=hc;
}

int setgolf(golf & s)
{
    std::cin.getline(s.fullname,len);
    if(s.fullname[0] == ''&& s.fullname[1] == '' && s.fullname[2] == '')
    return 0;
    else
    return 1;
}

void sethandicap(golf & s,int n )
{
    s.handicap = n;
}

void showgolf(const golf & s)
{
    std::cout<<"the full name :"<<s.fullname<<std::endl;
    std::cout<<"the handcape  :"<<s.handicap<<std::endl;
}

#include <iostream>
#include "sans.h"
int main()
{
    golf player;
    char name[len] = "santers God's men";
    int handicap = 84;
    setgolf(player,name,handicap);
    return 0;
}

//void setgolf(golf &,char * ,int);

setgolf(player,name,handicap);