C++ file readin with delimiters - c++

Question

Name~Proper Name~HR number~HD number~distance- format of the data in file
include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
string name;
string properName;
string hrN;
string hdN;
double distance;
ifstream fin;
string fileName;
cout << "Enter a file name: ";
getline(cin, fileName);
fin.open(fileName);
if(fin.fail())
{
cout << "Unable to open the file" << endl;
return -1;
}
else
{
string name;
string properName;
string hrN;
string hdN;
double distance;
string line;
string pN1;
bool found = false;
while(true)
{
getline(fin, name, '~');
getline(fin, properName,'~');
getline(fin, hrN,'~');
getline(fin, hdN, '~');
fin >> distance;
cout << "Enter a proper star name:";
string pN1;
cin >> pN1;
if(pN1.compare(properName))
{
found = true;
cout << "Star : "<< "proper name: "<<pN1<< "distance: "<<distance<<"light years" << "HD num: "<<hdN << "HR num: "<< hrN << "common name: "<< name << endl;
}
}
if (found == false)
{
cout << "No star with the properName"<<" "<< pN1 <<" "<<"was found"<< endl;
}
fin.close();
}
return 0;
}
This is what Ive got so far.
I'm just not sure how to store the variables, in order to search for a variable and display the contents of a specific line to the screen

Answer 1

There's quite a lot wrong with your code. You've duplicated the variable names for some reason, your input loop never terminates and you've asked the question about the star name inside the input loop. I'd say you're rushing into coding without thinking about what you are doing or knowing where you are going.
Lets take it one piece at a time.
The first thing you have is a bunch of related data about stars, name, proper name, distance etc. So lets express that fact by grouping the related data in a struct
struct StarData
{
string name;
string properName;
string hrN;
string hdN;
double distance;
};
Now lets write a loop that reads that data and importantly finishes when there is no more data
StarData data;
// loop until no more data
while (getline(fin, data.name, '~') && getline(fin, data.properName, '~') &&
getline(fin, data.hrN, '~') && getline(fin, data.hdN, '~') &&
(fin >> data.distance))
{
}
So this loop reads star data, one star at a time into the data variable. But as yet doesn't do anything with that data.
There are various ways to store the data so that it will be searchable, it's a very common thing to want to do, so C++ does most of the work for you. I'm going to use something called a std::map which is a data structure which is very good at storing data so it can be searched. Let modify the loop above
#include <map>
std::map<string, StarData> star_database;
StarData data;
// loop until no more data
while (getline(fin, data.name, '~') && getline(fin, data.properName, '~') &&
getline(fin, data.hrN, '~') && getline(fin, data.hdN, '~') &&
(fin >> data.distance))
{
// add star data to database using proper name as the key
star_database[data.properName] = data;
}
This code stores the star data in a variable called star_database. In particular because we keyed the map on the proper name, i.e. because we said star_database[data.properName] = data; later we'll be able to use the proper name to look up the data about the star.
Now we've done the while loop, lets ask the question about the star to look up, remember this happens after the while loop above, not inside it.
cout << "Enter a proper star name:";
string pN1;
cin >> pN1;
Now we'll do the lookup
auto answer = star_database.find(pN1); // lookup the proper name in the database
if (answer == star_database.end()) // did we find it?
{
cout << "No star with the proper name "<< pN1 <<" was found"<< endl;
}
else
{
cout << "Star : "<< "proper name: "<< pN1 <<
" distance: "<< answer->second.distance << " light years" <<
" HD num: "<< answer->second.hdN <<
" HR num: "<< answer->second.hrN <<
" common name: "<< answer->second.name << endl;
}
I've skipped over quite a lot of detail (I can only explain so much) but hopefully you've got the basic idea and can research the rest yourself.
All code untested, apologies in advance for any typos.