C++, Program ends before allowing input - c++

To practice C++ I am trying to make a simple program that allows a user to input a name followed by a score and then allows the user to enter a name and get the score that name was entered with. The program works fine until I enter an escape character (ctrl + z) once I'm done entering names, after entering the escape character the program will output the line "Enter name of student to look up the score" but not allow the user to input the name and instead reads out "Press any key to exit". I'm totally stumped on how to fix this and any help is greatly appreciated.
#include "stdafx.h"
#include <std_lib_facilities.h>
int main()
{
vector <string>names;
vector <int>scores;
string n = " "; // name
int s = 0; // score
string student = " ";
cout << "Enter the name followed by the score. (Ex. John 89)" << endl;
while(cin >> n >> s)
{
for(size_t i = 0; i < names.size(); ++i)
{
if(n == names[i])
{
cout << "Error: Duplicate name, Overwriting" << endl;
names.erase(names.begin() + i);
scores.erase(scores.begin() + i);
}
}
names.push_back(n);
scores.push_back(s);
}
cout << "Name: Score:" << endl;
for(size_t j = 0; j < names.size(); ++j)
{
cout << names[j];
cout <<" " << scores[j] << endl;
}
cout << "Enter name of student to look up their score" << endl;
cin >> student;
for(size_t g = 0; g < names.size(); ++g)
{
if(student == names[g])
{
cout << "Score: " << scores[g] << endl;
}
}
keep_window_open();
return 0;
}

After you press the CTRL+Z key combination, which induces an EOF state to the cin stream, you need to bring the cin input stream back to its normal 'good' state to be able to use it again.
Add the following code after your for loop where you print the contents of the vectors.
cin.clear();
You may also check the state of the standard input stream using the rdstate() function. Anything other than 0 means that the standard stream is in an error state.

As has been said, you need to clear the error state on std::cin after reading the records failed.
std::cin.clear();
should do the trick. Here's my take on this using
proper data structures instead of two isolated vectors
const correctness
separating functions
no more hacky .erase() calls with magic indexes
#include <map>
#include <iostream>
std::map<std::string, int> read_records()
{
std::map<std::string, int> records;
std::string name;
int score;
std::cout << "Enter the name followed by the score. (Ex. John 89)" << std::endl;
while(std::cin >> name >> score)
{
if (records.find(name) != end(records))
{
std::cout << "Error: Duplicate name, Overwriting" << std::endl;
} else
{
records.insert({name, score});
}
}
std::cin.clear();
return records;
}
int main()
{
auto const records = read_records();
std::cout << "Name\tScore:" << std::endl;
for(auto& r : records)
std::cout << r.first << "\t" << r.second << std::endl;
std::cout << "Enter name of student to look up their score: " << std::flush;
std::string name;
if (std::cin >> name)
{
std::cout << "\nScore: " << records.at(name) << std::endl;
}
}
If you required contiguous storage, use a flat_map like the one from boost.

Related

Error when passing vectors as parameter in Xcode

I'm working on a program that I've seen other people do online except I'm trying to use functions to complete it to make it somewhat more challenging for me to help me better understand pointers and vectors. The problem I'm having in xcode is I keep getting this error..
Expected ';' after top level declarator
right here on my code,
void showMenu(menuItemType (&menu_List)[8])[], vector<int> numbers) //<<< Error
{
cout << fixed << setprecision(2);
...
Where I am trying to use vector numbers in my function. Basically I want the numbers from the function passed back so that I can use them in another function I have not created yet. I've googled this error and it seems like no one can give a straight answer on how to fix this problem. Is anyone familiar with how to correct this? By no means is this code finished I'm just trying to get information regarding vectors as a parameter because from what I'm seeing syntax wise on other sites it looks to be correct. Thanks for your feedback.
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
#include <sstream>
#include <iterator>
using namespace std;
struct menuItemType{
string menuItem;
double menuPrice;
};
void getData(menuItemType (&mlist)[8]);
void showMenu(menuItemType (&menu_List)[8], vector<int> numbers);
int main() {
vector<int> temp;
menuItemType menuList[8];
getData(menuList);
showMenu(menuList,temp);
/*
cout << menuList[0].menuItem << " " << menuList[0].menuPrice << endl;
cout << menuList[1].menuItem << " " << menuList[1].menuPrice << endl;
*/
return 0;
}
void getData(menuItemType (&mlist)[8]){
string Str;
ifstream infile;
infile.open("cafe135.txt");
if(infile.is_open())
{
for (int i = 0; i < 8; ++i){
infile >> mlist[i].menuItem >> mlist[i].menuPrice;
}
}
else cout << "Unable to open file";
}
void showMenu(menuItemType (&menu_List)[8])[], vector<int> numbers)
{
cout << fixed << setprecision(2);
string choice;
cout << "Would you like to view the menu? [Y] or [N]: ";
cin >> choice;
cout << endl;
int x = 3;
int count = 1;
while (choice != "Y" && choice != "N" && choice != "y" && choice != "n")
{
if (count == 4){
return;
}
cout << "Error! Please try again ["
<< x
<< "] selections remaining: ";
cin >> choice;
cout << endl;
x--;
count++;
}
if (choice == "N" || choice == "n"){
return;
}
else
{
cout << "___________ Breakfast Menu ___________" << endl;
for (int i = 0; i < sizeof(menu_List)/sizeof(menu_List[0]); ++i)
{
cout << "Item "
<< (i+1)
<< ": "
<< menu_List[i].menuItem
<< " "
<< menu_List[i].menuPrice
<< endl;
}
cout << endl;
string itemSelection = " ";
//int str_length = 0;
cout << "Select your item numbers separated"
<< " by spaces (e.g. 1 3 5) Select 0 to cancel order: ";
cin.ignore();
getline(cin, itemSelection);
if (itemSelection == "0")
{
return;
}
vector<int> vectorItemSelection;
stringstream text_stream(itemSelection);
string item;
while (getline(text_stream, item, ' '))
{
vectorItemSelection.push_back(stoi(item));
}
int n = vectorItemSelection.size();
int arr[n];
for (int i = 0; i < n; i++)
{
arr[i] = vectorItemSelection[i];
}
}
}
Compare how menu_List is declared in this line
void showMenu(menuItemType (&menu_List)[8], vector<int> numbers);
and this line
void showMenu(menuItemType (&menu_List)[8])[], vector<int> numbers)
The first one is correct.
But I have to agree with the comments above, you are mixing up a lot of different things here. Just use vectors, 99% of the time it's the right thing to do anyway. and it's easier to learn one thing at a time.
Prefer to write your code like this
void getData(vector<menuItemType>&);
void showMenu(vector<menuItemType>&, vector<int> numbers);
int main() {
vector<int> temp;
vector<menuItemType> menuList(8);
...
See? Just use vectors everywhere.

Getting the input from the file as string and also integer C++

I have a text file. I have a text file consisting of member data. I am developing a program where we can get the member data from the file. After searching in the internet, I have searched a way to read all the data from the file as char array. But I want to change it where upon reading from file I want the data to be string and also integer.
name, icno, email, phone_number, acc_num, password ( read from file AS STRING )
month, year ( read from file AS INTEGER )
Content of Membership.txt
Mathavan|021127100897|MathavanKrishnan27#gmail.com|0167750575|1410065449|Mathavan1234|3|2022
Mathavan|021127100897|MathavanKrishnan27#gmail.com|0167750575|1410065448|Mathavan1234|3|2024
Mathavan|021127100897|MathavanKrishnan27#gmail.com|0167750575|1410065447|Mathavan1234|3|2022
string member_login(){
title();
fstream member;
member.open("Membership.txt",ios::in);
string pass_input, line, acc_num1, password1;
int login_attempt = 0, count = 0 , account = 0;
char dummy, resp, accno_input[25], name[25], icno[25],email [40], phone_number[25],acc_num[25],password[25],month[25], year[25];
account_num:
cout << " Enter your account number : ";
cin >> accno_input;
ifstream file("Membership.txt");
while (!file.eof()){
getline(file, line);
count++;
}
cout << accno_input;
int i = 0;
while(i <= count)
{
member.getline(name,25,'|');
member.getline(icno,25,'|');
member.getline(email,40,'|');
member.getline(phone_number,25, '|');
member.getline(acc_num,25, '|');
member.getline(password,25,'|' );
member.getline(month,25,'|' );
member.getline(year, 25);
cout << name << " ";
cout << icno << " ";
cout << acc_num << " ";
cout << accno_input;
if (acc_num == accno_input){
account = 1;
break;
}
i ++;
}
cout << account;
member.close();
if ( account != 1 ){
cout << endl;
cout << " Your account not found !!!"<< endl;
cout << " Please try again !!" << endl << endl;
cout << " PLEASE ENTER ANY KEY TO CONTINUE >>> ";
cin >> dummy;
goto account_num;
}
password1 = password;
cout << endl;
cout << " Enter your account password : ";
cin >> pass_input;
for (login_attempt = 1 ; login_attempt <= 2 ; login_attempt ++){
if (pass_input == password1){
cout << "Login Successful !!!";
break;
}
cout << endl;
cout << "Login Failed. Attempt " << login_attempt << " of 3" << endl;
cout << "Please re-enter Password: " ;
cin >> pass_input;
if (pass_input == password1){
cout << "Login Successful !!!";
break;
}
}
if ( login_attempt == 3){
cout << endl;
cout << "Login Failed. Attempt 3 of 3";
}
return accno_input;
}
There are so many things completely wrong in your program that I do recomend to you:
Delete and start from scratch.
There is no meaningful fix possible. There is even a goto. And you MUST stop using C-Style arrays with some agic dimension in C++. And C++ has many things to make your live easier. Simply use them.
Please find below a C++ solution.
You can copy and paste it and stay as you are, or, you take 3 hours and google all constructs and try to understand and learn and become a better programmer. Your choise.
#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
#include <vector>
#include <regex>
#include <iterator>
#include <algorithm>
const std::regex re{ R"(\|)" };
struct Member {
// Memeber data
std::string name{};
std::string icno{};
std::string email{};
std::string phoneNumber{};
std::string accountNumber{};
std::string password{};
int month{};
int year{};
// Extractor operator
friend std::istream& operator >> (std::istream& is, Member& m) {
// Readone complete line
if (std::string line{}; std::getline(is, line)) {
// Split it into parts
std::vector parts(std::sregex_token_iterator(line.begin(), line.end(), re, -1), {});
// assign parts to member data
if (parts.size() == 8) {
m.name = parts[0]; m.icno = parts[1]; m.email = parts[2]; m.phoneNumber = parts[3]; m.accountNumber = parts[4]; m.password = parts[5];
m.month = std::stoi(parts[6]); m.year = std::stoi(parts[7]);
}
}
return is;
}
};
// Filename for member data
const std::string fileName{ "r:\\Membership.txt" };
int main() {
// Open the data file and check, if it could be opened
if (std::ifstream fileStream{ fileName }; fileStream) {
// Read complete source file, parse it and get all data
std::vector memberData(std::istream_iterator<Member>(fileStream), {});
// We want the user to give 3 trials to enter valid data
constexpr unsigned int MaxTrials = 3u;
unsigned int numberOfTrials{};
// A valid input will stop the loop immediately
bool validInputgiven{};
// Now, try to get the correct input
while (not validInputgiven and numberOfTrials < MaxTrials) {
// Get an acoount number
std::cout << "\nEnter a account number: ";
std::string account{};
std::cin >> account;
// Check, if the account number is in the member data
if (std::count_if(memberData.begin(), memberData.end(), [&](const Member& m) { return m.accountNumber == account; }) > 0) {
// Account info wasOK. Get the password
std::cout << "\nEnter your password: ";
std::string password{};
std::cin >> password;
if (std::count_if(memberData.begin(), memberData.end(), [&](const Member& m) { return m.accountNumber == account and m.password == password; }) > 0) {
// Valid data found
validInputgiven = true;
std::cout << "\n\nEverything OK. Data validated.\n\n";
}
}
// Next try
++numberOfTrials;
if (not validInputgiven and numberOfTrials < MaxTrials) std::cout << "\nInvalid input. Please try again\n\n\n";
}
if (not validInputgiven ) std::cout << "\nToo many wrong tries. Aborting . . .\n\n\n";
}
else std::cerr << "\n\nError. Could not open source file '" << fileName << "'\n\n";
}

How to Accept [ENTER] key as an invalid input and send out error message

This is a program that grade user inputs for the questions of Driver's License Exam.
I'm having trouble of validating the user input.
I'd like to accept the [ENTER] key as an invalid input and proceed to my validation rather than just go to an empty line and cannot process to the next question. Purpose is to send out error message and that no input is given and [ENTER] key is not valid input and only accept one more chance to enter valid input which are a/A, b/B, c/C, or d/D. So that is why I'm using if statement here instead of loop.
I tried if (testTakerAnswers[ans] == (or =) '\n') {} but still doesn't solve the problem of newline.
I include curses.h in here hope to use getch() statement from the other post but somehow I can't manage to work in my code with an array instead of regular input.
I'm looking for other methods as well rather than getch()
So should I adjust my bool function, or directly validate input in main() function.
#include <iostream>
#include <iomanip>
#include <string>
#include <cctype>
#include <curses.h>
using namespace std;
const unsigned SIZE = 20; // Number of qns in the test
char testTakerAnswers[SIZE]; //Array to hold test taker's answers
bool validateInput(char);
class TestGrader
{
private:
char answers[SIZE]; // Holds the correct answers // Answer is array
int getNumWrong (char[]);
void missedQuestions (char[]);
public:
void setKey(string); // Initialize object with standard keys
void grade(char[]); // Grades the answers from tester
};
void TestGrader::setKey(string key){
if (key.length()!=SIZE){
cout << "Error in key data.\n";
return;
}
for (unsigned pos = 0; pos < SIZE ; pos ++)
answers [pos] = key [pos];
}
void TestGrader::grade(char test[])
{
int numWrong = getNumWrong(test);
if (numWrong <= 5)
cout << "Congratulations. You passed the exam.\n";
else
cout << "You did not pass the exam. \n";
cout << "You got " << (SIZE-numWrong) << " questions correct. \n";
if (numWrong > 0){
cout << "You missed the following " << numWrong << " questions: \n";
missedQuestions(test);
}
}
int TestGrader::getNumWrong(char test[])
{
int counter = 0;
for (int i = 0; i < SIZE; i++){
if (answers[i] != toupper(testTakerAnswers[i])){
counter++;
}
}
return counter;
}
void TestGrader::missedQuestions(char test[])
{
// cout << testTakerAnswers[i]; This is to print taker's answers
int counter = 0;
for (int i = 0; i < SIZE; i++){
if (answers[i] != toupper(testTakerAnswers[i])){
cout << "\n" << i + 1 << ". Correct answers: " << answers[i];
counter++;
}
}
}
bool validateInput(char ans){ // Only A, B, C, D valid input
if (toupper(ans)!='A' && toupper(ans)!= 'B' && toupper(ans)!='C' && toupper(ans)!= 'D'){
cout << "\n********************WARNING*******************\n";
cout << "Invalid input! Enter only a/A, b/B, c/C, or d/D\n";
return false;
}
if (testTakerAnswers[ans] == '\n'){
return false;
}
return true;
}
int main()
{
const int NUM_QUESTIONS = 20;
string name; //Test taker's name
char doAnother; //Control variable for main processing loop
TestGrader DMVexam; //Create a TestGrader object
DMVexam.setKey("BDAACABACDBCDADCCBDA");
do {
cout << "Applicant Name: ";
getline(cin,name);
cout << "Enter answer for " << name << ".\n";
cout << "Use only letters a/A, b/B, c/C, and d/D. \n\n";
for (int i = 0; i < NUM_QUESTIONS; i++){
// Input and validate it
do{
cout << "Q" << i+1 << ": ";
cin >> testTakerAnswers[i];
if (!validateInput(testTakerAnswers[i])){
cout << "You get one more chance to correct.\nOtherwise, it count as wrong answer.";
cout << "\n*********************************************";
cout << "\nRe-enter: ";
cin >> testTakerAnswers[i];
cout << '\n';
break;
}
}while(!validateInput(testTakerAnswers[i]));
}
//Call class function to grade the exam
cout << "Results for " << name << '\n';
DMVexam.grade(testTakerAnswers);
cout << "\nGrade another exam (Y/N)? ";
cin >> doAnother;
while (doAnother != 'Y' && doAnother != 'N' && doAnother != 'y' && doAnother != 'n'){
cout << doAnother << " is not a valid option. Try Again y/Y or n/N" << endl;
cin >> doAnother;}
cout << endl;
cin.ignore();
}while(doAnother != 'N' && doAnother != 'n');
return 0;
}
Your issue is cin >> testTakerAnswers[i]; cin is whitespace delimited, that means that any whitespace (including '\n') will be discarded. So testTakerAnswers[i] can never be '\n'.
I'm not sure exactly what you want to do, but possibly try
getline(cin,input_string);
then
input_string == "A" | input_string == "B" | ...
So if only the enter key is pressed, input_string will become "".

c++ input for-loop followed by another input

c++ Microsoft visual studio on a windows.
im very new to coding. currently going through Programming -- Principles and Practice Using C++ by Stroupstrup and I came across a difficulty. I am to create a "score chart" with vector name and vector score from the user input. I used for-loop to get the input. now I am to modify the program so that with 2nd input from the user I can search the list and "cout<<" the score for a person. the problem is the the program completely ignores the 2nd "cin>>" command.
I search online and could not find a reasonable answer to this problem. Is there any special interaction between a for-loop input being terminated and another input (not looped)
syntax:
#include "stdafx.h"
#include <iostream>
#include <vector>
#include <string>
using namespace std;
int main()
{
vector<string> name;
vector<int> score;
string temp2;
int i;
for (string temp; cin >> temp >> i;) //input terminated with "Ctrl+Z"
name.push_back(temp), score.push_back(i);
for (int i = 0; i < name.size(); ++i) {
for (int j = i + 1; j < name.size(); ++j) {
if (name[i] == name[j]) {
name[j] = "error";
score[j] = 0;
}
}
}
for (int i = 0; i < name.size(); ++i) {
cout << name[i] << "------" << score[i] << "\n";
}
cout << "name"; //this line shows in the console
cin >> temp2; //but I cannot prompt the user to input again?
return 0;
}
CTRL-Z is interpreted as "End-Of-File", such that any subsequent access to this stream will not read in items any more. The only secure way is to change program logic such that the list of names is terminated by, let's say "END", and not a CTRL-Z. Then you can continue in a save manner.
Often input from a terminal is read in line by line and parsed afterwards. This makes error handling easier. See the following code following such an approach:
#include <sstream>
int main() {
string line;
map<string,int> scoreboard;
cout << "enter name score (type END to finish):" << endl;
while (std::getline(cin, line) && line != "END") {
stringstream ss(line);
string name;
int score;
if (ss >> name >> score) {
scoreboard[name] = score;
} else {
cout << "invalid input. Type END to finish" << endl;
}
}
cout << "enter name:" << endl;
string name;
if (cin >> name) {
auto item = scoreboard.find(name);
if (item != scoreboard.end()){
cout << "score of " << name << ":" << item->second << endl;
}
else {
cout << "no entry for " << name << "." << endl;
}
}
}

Why am I getting this error message? C++

I am getting this error every time I try to run my program.
This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
terminate called after throwing an instance of
'std::logic_error' what(): basic_string::_M_construct null not valid
#include <iostream>
#include <string>
using namespace std;
struct Bin
{
string desc;
int partsQty;
};
void addParts(Bin bList[], int i);
void removeParts(Bin bList[], int i);
int main() {
char response;
int binNumber;
const int NUM_OF_BINS = 11;
Bin binList[NUM_OF_BINS] = {
{0,0},
{"Valve", 10},
{"Earing",5},
{"Bushing",15},
{"Coupling",21},
{"Flange",7},
{"Gear",5},
{"Gear Housing",5},
{"Vaccum Gripper",25},
{"Cable",18},
{"Rod",12}
};
for(int i=1;i < 11;i++)
{
cout << "Bin #" << i << " Part: " << binList[i].desc << " Quantity " << binList[i].partsQty << endl;
}
cout << "Please select a bin or enter 0 to terminate";
cin >> binNumber;
cout << "Would you like to add or remove parts from a certain bin?(A or R)";
cin >> response;
if(response == 'a')
addParts(binList, binNumber);
else if(response == 'r')
removeParts(binList, binNumber);
return 0;
}
void addParts(Bin bList[], int i)
{
int parts;
int num;
cout << "How many parts would you like to add?";
cin >> num;
parts = bList[i].partsQty + num;
cout << "Bin # " << i << " now contains " << parts << " parts";
}
void removeParts(Bin bList[], int i)
{
int parts;
int number;
cout << "Which bin would you like to remove parts to?";
cin >> i;
cout << "How many parts would you like to remove?" << endl;
cin >> number;
parts = bList[i].partsQty - number;
if(parts < 0)
cout << "Please enter a number that isn't going to make the amount of parts in the bin negative.";
cin >> number;
parts = bList[i].partsQty - number;
cout << "The remaining amount of parts in bin #" << i << " is " << parts;
}
It comes from:
{0,0}
in your list of initializers for binList. 0 is not a correct initializer for std::string. You could perhaps use {"", 0} instead, or even {}.
Another idea might be to revise your program logic so that you do not require a dummy entry at the start of the array.