How to determine if name and lname is not in file - c++

Question

The program, is basically sussposed to iterate a file containing the elements
Harry Keeling [phone]
Frank James [phone]
Arthur Paul [phone]
Todd Shurn [phone]
Richard Okpala 202 388 410
what my current program is outputting the phonenumber if firstname and lastname is present in file but if its nothow do i output phone number isnt here my current code.
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
void lookup_name(ifstream&, string&, string&, string&); // prototype
int main()
{
ifstream myfile;
string name, lastname, phonenumber;
char choice;
do
{
myfile.open("infile.txt");
cout << "What is the First name? " << endl;
cin >> name;
cout << "what is your last name?" << endl;
cin >> lastname;
lookup_name(myfile, name, lastname, phonenumber);
cout << "Do you want to lookup another name<Y/N" << endl;
cin >> choice;
} while (choice == 'Y');
return 0;
}
void lookup_name(ifstream& myfile, string& name, string& lastname, string& phonenumber)
{
string name1, name2, fullname, secondname, dummy;
for (int i = 0; i < 5; i++) {
myfile >> name1 >> name2;
fullname = name1 + name2;
secondname = name + lastname;
if (fullname == secondname) {
myfile >> phonenumber;
cout << phonenumber << endl;
myfile.close();
break;
}
else if (fullname != secondname) {
myfile >> dummy;
phonenumber = dummy;
}

Answer 1

Just return whether you found it or not from your lookup function
int lookup_name(ifstream& myfile, string& name, string& lastname, string& phonenumber)
{
string name1, name2, fullname, secondname, dummy;
for (int i = 0; i < 5; i++) {
myfile >> name1 >> name2;
fullname = name1 + name2;
secondname = name + lastname;
if (fullname == secondname) {
myfile >> phonenumber;
cout << phonenumber << endl;
myfile.close();
return 1;
}
else if (fullname != secondname) {
myfile >> dummy;
phonenumber = dummy;
}
}
return 0;
}
Then use the return value
if ( ! lookup_name(myfile, name, lastname, phonenumber) ) {
cout << "Nope, didn't find it!" << endl;
}