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)
bit∙hub [bit-huhb] n. A source and destination for information.
thanks......that worked.....
Consider using std::string rather than char* for strings, too.
Originally Posted by Adak
Specifically..
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 <string> void combio(std::string const& message, vt& x)
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(); }
Warning: Have doubt in anything I post.
GCC 4.5, Boost 1.40, Code::Blocks 8.02, Ubuntu 9.10 010001000110000101100101
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
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.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
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.
Last edited by King Mir; 09-01-2009 at 08:22 PM.
It is too clear and so it is hard to see.
A dunce once searched for fire with a lighted lantern.
Had he known what fire was,
He could have cooked his rice much sooner.
3) It's usually not portable since you have to target specific executables located on specific OSes instead of relying on standard C++.
