I am trying to create 2D array of structures and print the value. How "Segmentaion fault (core dumped)" message".
#include <iostream>
#include <string>
using namespace std;
struct student{
string name;
int age;
float marks;
};
student* initiateStudent(string name, int age, float marks){
student *studFun;
studFun->name = name;
studFun->age = age;
studFun->marks = marks;
return studFun;
}
int main() {
int totalStudents = 1;
string name;
int age;
float marks;
cin >> totalStudents;
student** stud = new student*[totalStudents];
for(int i=0;i<totalStudents;i++){
stud[i] = new student[1];
cin >> name >> age >> marks;
stud[i] = initiateStudent(name,age,marks);
}
delete [] stud;
return 0;
}
I am compiling it using Netbeans for C++. Can anyone tell me whats wrong with this code ?
This should work
#include <iostream>
#include <string>
using namespace std;
struct student{
string name;
int age;
float marks;
};
student* initiateStudent(string name, int age, float marks){
student *studFun = new student();
studFun->name = name;
studFun->age = age;
studFun->marks = marks;
return studFun;
}
int main() {
int totalStudents = 1;
string name;
int age;
float marks;
cin >> totalStudents;
student** stud = new student*[totalStudents];
for(int i=0;i<totalStudents;i++){
stud[i] = new student[1];
cin >> name;
cin >> age;
cin >> marks;
stud[i] = initiateStudent(name,age,marks);
}
delete [] stud;
return 0;
}
Related
Here the below code is my some part of my program. It doesn't execute it says c++ forbids converting string constants to char*.How can I fix this error?
#include <cstring>
#include <iostream>
using namespace std;
class Bank
{
private:
char name[20];
int acc;
float amount;
public:
Bank()
{
strcpy("",name);
acc = 0;
amount = 0;
}
void open(int a)
{
cout << "Enter name:";
cin >> name;
acc = a;
cout << "Enter Amount" << endl;
cin >> amount;
}
void edit(int flag, float a);
};
int main()
{
Bank B[10];
}
std::strcpy("", name); needs to be std::strcpy(name, "");
Although, setting aside the fact that std::string would be a far better type for name (the future King of England, Charles Mountbatten-Windsor, would not be able to be a customer), writing
name[0] = 0;
would be sufficient.
I have a project in my C++ class - we're supposed to make a "simple student management system" comprised of a class for the student attribute variables, and a main function with a branch statement that lets the user input names and IDs for the students. I know that I need to use an array to make "slots" for the students, and that my branch statements need to let the user input values into those slots, but I'm not exactly sure how to do it. Here is the code that I have so far.
#include <string>
#include <iostream>
#include <utility>
using std::string;
using std::cin;
using std::cout;
using std::endl;
struct Student {
private:
int id;
string name;
int birthday;
public:
Student()
{
id = 0;
birthday = 0;
}
Student(int id, string name, int birthday)
{
//set your parameters to the class variables
this->id = id;
this->name = name;
this->birthday = birthday;
}
void setID(int id)
{
this->id = id;
}
int getID() {
return id;
}
void setName(string name)
{
this->name = name;
}
string getName()
{
return name;
}
void setBirthday(int birthday)
{
this->birthday = birthday;
}
int getBirthday()
{
return birthday;
}
void output() {
cout << id << name << birthday << endl;
}
};
int main() {
Student arr[50];
cout << "Student Management System" << endl;
cout << "Press 'a' to add a student" << endl;
char a = 1;
int y = 1;
while (a == 'a') {
switch (y)
{
cout << "Input Student ID:";
cin >> id;
}
}
}
What I'm focusing on most is the fourth line from the bottom. I was told that I need to use my setters, so I said that I want what my user inputs to be treated as the value of the ID variable that I set in the class. However, when I wrote this out, I was given an error. Could someone tell me what the issue is?
You should try to get your switch statement working correctly. To use classes setters, you can store the user input to a temporary variable then from your one student you can call the member function. i.e. in your case:
arr[index].setID(tempInputVariable);
There is no id in your main function or as a global variable.
I suggest you overload operator >> to have your structure extract its members from the data stream:
struct Student
{
//...
public:
friend std::istream& operator>>(std::istream& input, Student& s);
};
std::istream& operator>>(std::istream& input, Student& s)
{
input >> s.id;
input >> s.name;
input >> s.birthday;
return input;
}
Although the above code doesn't use setters, it is the preferred method for inputting data.
The overload can be modified to use setters (kind of overkill):
std::istream& operator>>(std::istream& input, Student& s)
{
int id;
input >> id;
s.setID(id);
std::string name;
input >> name;
s.setName(name);
int birthday;
input >> birthday;
s.setBirthday(birthday);
return input;
}
If you don't like the overload, you can perform the steps in your main function:
//...
Student new_student;
//...
{
int student_id;
std::cout << "Input Student ID:";
std::cin >> student_id;
new_student.setID(student_id);
std::string student_name;
std::cout << "Input Student Name: ";
std::cin >> student_name;
new_student.setName(student_name);
int student_birthday;
std::cout << "Input Student Birthday: ";
std::cin >> student_birthday;
new_student.setBirthday(student_birthday);
}
Edit 1: The Database
You'll probably need to store or remember the students. This is easy using the first method above:
std::vector<Student> database;
Student s;
std::cout << "Enter student information (ID, Name and birthday, separated by spaces:\n";
std::cin >> s;
// Append to the database
database.push_back(s);
If you haven't learned std::vector you can try an array:
const size_t MAXIMUM_STUDENTS = 16;
Student database[MAXIMUM_STUDENTS];
size_t database_index = 0;
//...
Student s;
std::cout << "Enter student information (ID, Name and birthday, separated by spaces:\n";
std::cin >> s;
// Append to database
database[database_index] = s;
++database_index;
I recently started learning c++ so I'm still learning. Basically I'm trying to read my text file when the string "NEW_EMPLOYEE" is found and then store every line into their respective member variables until an empty line is found in the text file to stop. The problem I'm having is how can I use getline to import each line into each variable of my class "Employee" all at once? Should I use istringstream instead?
My text file called "employee.txt"
NEW_EMPLOYEE
460713
John
Smith
64000
36
END_OF_FILE
My class Employee:
class Employee {
private: //Member variables
int ID;
string FirstName;
string LastName;
int Salary;
int Hours;
public:
Employee() {} //Default constructor
Employee(int& id, string& firstName, string& lastName, int& salary, int& hours) {
ID = id;
FirstName = firstName;
LastName = lastName;
Salary = salary
Hours = hours;
}
};
My main.cpp:
#include <iostream>
#include <fstream>
int main() {
Employee employee;
int id;
string firstName;
string lastName;
int salary;
int hours;
string line;
ifstream employeeFile;
employeeFile.open("employee.txt");
while(getline(employeeFile, line)) {
if(line == "NEW_EMPLOYEE") {
do {
//Don't know what to do here???
} while (!line.empty());
}
}
employeeFile.close();
return 0;
}
The straightforward approach would be to do something like that
while(employeeFile >> line){
if(line != "NEW_EMPLOYEE") continue;
int id,salary,hours;
string firstName, lastName;
employeeFile >> id >> firstName >> lastName >> salary >> hours;
Employee employee = Employee(id, firstName, lastName, salary, hours);
// Do what you want with employee
}
This assumes that the data are written in the file always in the same order. I also assumed that the lines contain no spaces since they're either numbers or names so I used >> operator. You can use getline instead if that's not the case.
If you always sure the data are in the same order then this should be enough. If that's not true, I'd recommend writing the object as JSON in the file, and use a JSON parser library to read the file directly into an object.
yes..straight forward approach can help you otherwise u can use simple method like ...
#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <sstream>
using namespace std;
int main() {
string x[100];
int i=0;
// Employee employee;
int id;
string firstName;
string lastName;
int salary;
int hours;
string line;
string text;
ifstream employeeFile;
employeeFile.open("employee.txt");
while(!employeeFile.eof())
{
getline(employeeFile,text);
x[i++]=text;
}
// employeeFile.close();
stringstream(x[1]) >> id; //string to int
firstName = x[2];
lastName = x[3];
stringstream(x[4]) >> salary;
stringstream(x[5]) >> hours;
//cout<<id<<" "<<firstName;
}
Then you can call your method . But straight forward approach is moore perfect than this :)
I'm quite new with c++ and need some help with the following code.
#include <iostream>
using namespace std;
struct student {
string name;
int age;
float marks;
};
struct student *initiateStudent(string , int , float);
int main ( ) {
int totalStudents = 1;
string name;
int age;
float marks;
cin >> totalStudents;
student *stud[totalStudents];
for( int i = 0; i < totalStudents; i++ ) {
cin >> name >> age >> marks;
stud[i] = initiateStudent(name,age,marks);
}
cout << stud[0]->name;
return 0;
}
struct student *initiateStudent(string name, int age, float marks)
{
student *temp_student;
temp_student->name = name;
temp_student->age = age;
temp_student->marks = marks;
return temp_student;
}
I need in the function initiateStudent return a struct pointer to the pointer array stud by passing the members name, age, marks.
I know that the problem sofar is the fact that temp_student is destroyed when I return to the main file.
So my question is how it could be done by just passing the members of the struct and then return back with information to the pointer array stud.
Thank you very much.
Semi-answer To explain the bad habits:
#include <string>
#include <iostream>
#include <vector>
//using namespace std; often injects subtle bugs. Use with caution
// read more here:
// http://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice
struct student
{
std::string name; // explicit namespacing reduces possibility of unwanted collisions
int age;
float marks;
//added constructor in place of initialization function.
student(std::string name, int age, float marks):name(name), age(age), marks(marks)
{
}
};
int main()
{
int totalStudents = 1;
std::string name;
int age;
float marks;
while (!(std::cin >> totalStudents)) // testing input for success
// Needed extra brackets caught by M.M
// teach me to not test even a throw-away example
{
std::cout << "must... have... good... input..." << std::endl;
cin.clear(); // clear the error and get rid of any other garbage the user may have input.
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
//student *stud[totalStudents]; illegal in C++
std::vector<student *> stud(totalStudents); // using dynamic array instead
for (int i = 0; i < totalStudents; )// i++ removed
{
if (std::cin >> name >> age >> marks) //testing input
{
stud[i] = new student(name, age, marks); // using constructor
i++; // and put here. Only increment if input is valid.
}
else
{
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
}
std::cout << stud[0]->name;
for (student * stu: stud) // cleaning up allocated memory
{
delete stu;
}
return 0;
}
One of the beauties of C++ is you rarely need to self-manage memory. In fact there are huge advantages in not doing it above and beyond not having to clean up after yourself.
#include <string>
#include <iostream>
#include <vector>
struct student
{
std::string name;
int age;
float marks;
student(std::string name, int age, float marks):name(name), age(age), marks(marks)
{
}
};
int main()
{
std::string name;
int age;
float marks;
std::vector<student> stud; // look ma! No pointer!
while (std::cin >> name >> age >> marks) //exits loop on bad input
{
stud.emplace_back(name, age, marks); // building directly in vector
// vector will size itself as needed.
}
std::cout << stud[0].name;
return 0;
}
One more caveat: >> is whiespace delimited. That means it stops when it finds whitespace (space, tab, end of line...) so a name of "John Jacob Jingleheimer-Shmidt" will go into name as "John". >> will then attempt to interpret "Jacob" as age, and that will not go so well.
the simple solution is to make your initiateStudent() creates temp_student on the heap (with new): and returns it. keep in mind heap allocated memory is not freed automatically so don't forget to free it later on yourself.
#include <iostream>
#include <string>
using namespace std;
struct student {
string name;
int age;
float marks;
};
struct student *initiateStudent(string , int , float);
int main ( ) {
int totalStudents = 1;
string name;
int age;
float marks;
cout << "Total student: ";
cin >> totalStudents;
cin.sync(); // very very important to not affect the next input (name)
student* stud = new student[totalStudents];
for( int i = 0; i < totalStudents; i++ )
{
cout << "Name: ";
getline(cin, name);
cin.sync();
cout << "age: ";
cin >> age;
cout << endl;
cout << "Marks: ";
cin >> marks;
cout << endl;
cin.sync();
stud[i] = *initiateStudent(name, age, marks);
}
cout << "Student 1: " << stud[0].name << endl;
delete[] stud;
stud = NULL;
return 0;
}
struct student *initiateStudent(string name, int age, float marks)
{
student *temp_student = new student;
temp_student->name = name;
temp_student->age = age;
temp_student->marks = marks;
return temp_student;
}
In the code below I am trying to have the variable fullName be populated with whatever I enter during the operation of the function namecheck. I am not sure where I am going wrong. Please help and thank you for it.
#include <cstdlib>
#include <iomanip>
#include <iostream>
#include <cmath>
#include <string>
#include <fstream>
using namespace std;
string namecheck();
int main()
{
cout<<fixed;
string firstName;
string lastName;
string fullName;
char action;
int pin;
int pinTry =1;
int actionsTaken =0;
int joeyPin = 4433;
int mildredPin = 2849;
double joeyTotal = 3742.55;
double mildredTotal = 19.36;
double withdraw;
double deposit;
namecheck();
cout<<fullName;
}
string namecheck(){
string firstName;
string lastName;
string fullName;
string completeName;
double joeyTotal = 3742.55;
double mildredTotal = 19.36;
cout<<"Welcome to Blah National Bank!\n";
cout<<"What is your first name?\n";
cin>>firstName;
if (firstName == "END"){
cout<<"User totals: \n"
<<"Joey Stowy:\t"<<setprecision(2)<<joeyTotal<<endl<<endl
<<"Mildred Moredebt:\t"<<setprecision(2)<<mildredTotal<<endl<<endl;
}
if (firstName != "END"){
cout<<"What is your last name?\n";
cin>>lastName;
}
fullName = firstName+" "+lastName;
return fullName;
}
Change:
namecheck();
cout<<fullName;
to:
fullname = namecheck();
cout<<fullName()
.
When you call namecheck() in main, assign the result to fullName:
fullName = namecheck();