Ignoring assignment

In the given program, value of x does not change as per input given by user. It assigns x= 2 automatically and prints the same. What is the reason ?

Code:

---

#include <iostream>

using namespace std;
template <class vt>
 
   
void combio(char *message,vt x)
{
   
    cout << message;
    cin >> x;
   
}

int main()
{
  int x;
 
  combio<int>("please enter a value",x);
    cout << x;



    system("PAUSE");
    return 0;
}

---

x is passed by value. Pass by reference instead.

Code:

---

void combio(char *message,vt& x)

---

thanks......that worked.....

Consider using std::string rather than char* for strings, too.

Quote:

---

Originally Posted by Elysia

Consider using std::string rather than char* for strings, too.

---

Specifically..

Code:

---

#include <string>
void combio(std::string const& message, vt& x)

---

Also consider not using system. You could use cin.get to pause, as long as the stream is empty, which is what cin.ignore does. An on-the-go method would be cin.ignore(1000, '\n'); cin.get(); but something like this works:

Code:

---

#include <limits>
#include <ios>

void pause()
{
  if(!std::cin.good())
    std::cin.clear();

  std::cout << "Press the return key to continue..." << std::endl;

  std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
  std::cin.get();
}

---

Quote:

---

Originally Posted by Dae

Also consider not using system. You could use cin.get to pause, as long as the stream is empty, which is what cin.ignore does. An on-the-go method would be cin.ignore(1000, '\n'); cin.get(); but something like this works:

---

Just out of curiousity, what is the reasoning for not using system? Not to be argumentative, just genuinely curious. I use two commands with system, namely CLS and PAUSE, mostly because it is a convienient, one line command, that works correctly each time. If there's a reason not to use it, I should probably learn another way to do that :D

Quote:

---

Originally Posted by kalor_alros

Just out of curiousity, what is the reasoning for not using system? Not to be argumentative, just genuinely curious. I use two commands with system, namely CLS and PAUSE, mostly because it is a convienient, one line command, that works correctly each time. If there's a reason not to use it, I should probably learn another way to do that :D

---

1) It's horribly inefficient. You are starting another program just to wait for user input. That's a lot of overhead compared to the alternative.

2) it's a security vulnerability, because under certain conditions the programs called by system can be made to refer to a malicious program, instead of the intended one.

3) It's usually not portable since you have to target specific executables located on specific OSes instead of relying on standard C++.