#include <iostream>

#include <fstream>

#include <vector>

#include <string>

// Exception object to thrown when a client attempts to

// open a text file via a name that does correspond to a

// file in the current working directory.

class FileNotFoundException : public std::exception {

std::string message; // Identifies the exception and filename

public:

// Constructor establishes the exception object's message

FileNotFoundException(const std::string& fname):

message("File \"" + fname + "\" not found") {}

// Reveal message to clients

const char *what() const {

return message.c_str();

}

};

// Creates and returns a vector of integers from data stored

// in a text file.

// filename: the name of the text file containing the data

// Returns a vector containing the data in the file, if possible

std::vector<int> load_vector(const std::string& filename) {

std::ifstream fin(filename); // Open the text file for reading

if (fin.good()) { // Did the file open successfully?

int n;

fin >> n; // Size of data set

std::vector<int> result(n); // Allocate space for the vector

int value, i = 0;

while (fin >> value)

result.at(i++) = value; // Append it to the vector

return result; // Return the populated vector

}

else // Could not open the text file

throw FileNotFoundException(filename);

}

int main() {

try {

std::vector<int> numbers = load_vector("values.data");

for (int value : numbers)

std::cout << value << ' ';

std::cout << '\n';

}

catch (std::out_of_range& e) {

std::cout << "Error: vector bounds exceeded\n";

std::cout << e.what() << '\n';

}

catch (FileNotFoundException& e) {

std::cout << "Error: cannot open file\n";

std::cout << e.what() << '\n';

}

}