quit program when character q is entered

[tdleanz]

Hello, I am trying to exit the program if the character 'q' is entered into input. I am expecting an integer value for input. I am confused on the best way to go about this. I tried atoi but had no luck. Would a switch statement work better for me?

// Still need program to exit if character q is entered

// still need program to exit if say a big number like 50000000000 is entered,
// stop computation at 35000000 
// if user enters character s

#include <iostream>
#include <cstdlib>
#include <cmath>
#include <iomanip>
#include <string>


#define PI 3.14

using namespace std;

int main(){
// for the program to keep executing until control + c is pressed, or 'q' is entered
bool done = false;
int input;


while(!done){

std::cout << "Please enter an integer or 'q' to quit" << std::endl;



// user input
cin >> input;

if(input == 'q')
	done = true;
	break;


std::cout << "You have asked to compute the square root of PI " << input <<  " times:" << std::endl;

	// for loop to increment number output
	for(int i = 0; i < input; i++){
		std::cout << (i+1) << std::endl;
	}

	double calculatePi;
	calculatePi= sqrt(PI);

	std::cout << "The square root of PI is " << setprecision(3) << calculatePi << "." << std::endl;

	}
}

[An Integer]

This is what you missed. So you are trying to check if an integer equals a string.

int main(){
	while (true) {
		int command;   // Should be string command if we want to launch if-statement.
		cin >> command;

		if (command == "q") {   // This will not work
			break;
		}
	}
}

However, this would work perfectly fine:

int main(){
	while (true) {
		string command;    // Now it's a string!
		cin >> command;

		if (command == "q") {
			break;
		}
	}
}

In your case you are trying to make the program see if an Integer = "q", which doesn't make much sense. Therefor, you have to set the input as a string and then convert it into an integer so it makes sense for your code. Take a look:

int main(){
	string choice;
	double PI = 3.14;

	while (true) {

	std::cout << "Please enter an integer or 'q' to quit" << std::endl;
	cin >> choice;

	if (choice == "q") {
		break;
	}
	else {
		int input = atoi(choice.c_str());     // Converting string to integer

		std::cout << "You have asked to compute the square root of PI " << input << " times:" << std::endl;

		for (int i = 0; i < input; i++) {
			std::cout << (i + 1) << std::endl;
		}

		double calculatePi;
		calculatePi = sqrt(PI);

		std::cout << "The square root of PI is " << setprecision(3) << calculatePi << "." << std::endl;
		}

	}
}

The code above should work!

[tdleanz]

awesome, thank you very much!

Also, say a big number like 5 million is entered by the user, and I don't want to go all the way to 5 million, i want to stop at 1 million. If i press the character 's', how do i stop the computation immediately and display the last computation I did, before display sqrt of pi? would i just use the peek function to read any input? the program will then come back and ask for input again

[An Integer]

A little uncertain of what you are requesting. For storing something with a spesific set of digits or letters, you could use char array. For example char bignumber[50]. Maybe it would need some specifications if you still want to keep the amount of characters the same but not exceed a certain number. Ergo, 1 million instead of 5 million, considering that they both have 7 digits. You can read more about this here, http://www.cplusplus.com/doc/tutorial/ntcs/.

When it comes to the "press the character 's'" part you could do something like this:

vector<char> values;

int main(){
	char addDigit;

	while (cin >> addDigit) {
		if (addDigit == 's') {
			break;
		}
		else {
			values.push_back(addDigit);
		}
	}

	cout << "Your total values is: ";
	for (int i = 0; i < values.size(); ++i) {
		cout << values[i];
	}
	cout << "\n" << endl;

	return 0;
}

You could also make the whole vector one single variable instead of printing it out like I did here. From the code above you can start making out what is- and not permitted inside the vector. For example, the first char can only be between 1-4 or something. As shown below:

vector<char> values;

int main(){
	char addDigit;

	while (cin >> addDigit) {          // Keep adding digits to vector unless
		if (addDigit == 's') {         // We press 's' to end the loop.
			break;
		}
		else {
			values.push_back(addDigit);
		}
	}

	if (values[0] != 1) {      // The first value we entered must be a 1
		cout << "You must start with a 1" << endl;
	}
	else {   // Displaying the values by printing them out, but only if first value was a 1
		cout << "Your total values is: ";
		for (int i = 0; i < values.size(); ++i) {
			cout << values[i];
		}
		cout << "\n" << endl;
	}

	return 0;
}

[tdleanz]

So this is all i need to do now "Now if the user entered a huge number by mistake and wants stop the computation in the middle! The only way to stop your basic program in the middle of a computation is to use Ctrl C, which would brutally kill your program. Design and implement your program so that users can stop any computation in the middle by entering ‘s’. Your program will stop gracefully the current computation and display the prompt:

Please enter an integer or ‘q’ to quit."

this is what I have. How would i go about doing this? Thanks!!

// still need program to exit if say a big number like 50000000000 is entered,
// stop computation at 35000000 
// if user enters character s

#include <iostream>
#include <cstdlib>
#include <cmath>
#include <iomanip>
#include <string>
#include <cstring>

#define PI 3.14

using namespace std;

int main(){
// for the program to keep executing until control + c is pressed, or 'q' is entered
bool done = false;
string choice;
string input;

while(!done){

std::cout << "Please enter an integer or 'q' to quit" << std::endl;



// user input
cin >> choice;

if(choice == "q"){
	break;
}else{

		int input = atoi(choice.c_str());     // Converting string to integer

std::cout << "You have asked to compute the square root of PI " << input <<  " times:" << std::endl;
		
			// for loop to increment number output
			for(int i = 0; i < input; i++){
				std::cout << (i+1) << std::endl;
			}

			double calculatePi;
			calculatePi= sqrt(PI);

			std::cout << "The square root of PI is " << setprecision(3) << calculatePi << "." << std::endl;

			}
		}
	}

[An Integer]

Are you thinking about a key stroke? See this:

#include <Windows.h>
#include <concrt.h>

vector<char> values;

int main(){
	char addDigit;

	while (cin >> addDigit) {
		if (addDigit == 's') {
			break;
		}
		else {
			values.push_back(addDigit);
		}
	}

	cout << "Your total values is: ";
	for (int i = 0; i < values.size(); ++i) {
		cout << values[i] << endl;
		Concurrency::wait(500);

		if (GetKeyState('S') & 0x8000) {
			break;
		}
	}
	cout << "\n" << endl;

	return 0;
}

Check out https://stackoverflow.com/questions/41600981/how-do-i-check-if-a-key-is-pressed-on-c for more

[tdleanz]

I don't really know how to go about this. so if the user enters 's', how do i stop current computation and ask for input again?