How to end my while loop? [duplicate] - c++

Question

This question already has answers here:
Immediate exit of 'while' loop in C++ [closed]
(10 answers)
Closed 6 years ago.
Hey can anyone lend me a hand? How can I make my loop end after the first calculation? After i complete one calculation such as addition, I would like to end it. Sorry for the noobie questions. I'm just learning loops now in my class. Greatly appreciated.
#include <iostream>
#include <string>
using namespace std;
int main()
{
int numOne;
int numTwo;
int result;
string operation;
cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
while (operation == "e" || operation == "E")
{
cout << "Operation type invalid." << endl;
cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
}
while (operation == "+" || operation == "-" || operation == "*" || operation == "/")
{
cout << "Please enter integer one: ";
cin >> numOne;
cout << "Please enter integer two: ";
cin >> numTwo;
if (operation == "+")
{
result = numOne + numTwo;
cout << "The numbers you entered were " << numOne << "," << numTwo << endl;
cout << "The operation you chose was " << operation << "." << endl;
cout << "The operations result is " << result << "." << endl;
cout << "Your equation was: " << numOne << " " << operation << " " << numTwo << " = " << result << ".";
}
else if (operation == "-")
{
result = numOne - numTwo;
cout << "The numbers you entered were " << numOne << "," << numTwo << endl;
cout << "The operation you chose was " << operation << "." << endl;
cout << "The operations result is " << result << "." << endl;
cout << "Your equation was: " << numOne << " " << operation << " " << numTwo << " = " << result << ".";
}
else if (operation == "*")
{
result = numOne * numTwo;
cout << "The numbers you entered were " << numOne << "," << numTwo << endl;
cout << "The operation you chose was " << operation << "." << endl;
cout << "The operations result is " << result << endl;
cout << "Your equation was: " << numOne << " " << operation << " " << numTwo << " = " << result << ".";
}
else if (operation == "/")
{
if (numTwo == 0)
{
cout << "You cannot divide by zero!" << endl;
}
else
{
result = numOne / numTwo;
cout << "The numbers you entered were " << numOne << "," << numTwo << endl;
cout << "The operation you chose was " << operation << "." << endl;
cout << "The operations result is " << result << endl;
cout << "Your equation was: " << numOne << " " << operation << " " << numTwo << " = " << result << ".";
}
}
}
return 0;
}
I'm not allowed to use break. Is there another way?

Answer 1

You can end a while loop using...
break;
ie
if(!(operation == "e" || operation == "E")) {
break;
}
Normally to end a while loop the (EXPRESSION) in the following ie
while((EXPRESSION) == true) { execute_code_here();}
needs to evaluate to false. The expression can be made up of many logical pieces ie
while (a == b && c != d && f++ < 1000) {do_something_here();}
The break keyword is used to terminate a while loop early but this can also be achieved by adding something to the expression that allows you to terminate the while loop ie make the expression evaluate to false, this is normally done using a flag or a counter.
To achieve the same effect as break without using it you can use this technique with continue. You then use the flag or counter along with continue to achieve the same thing as break ie, this is a counter example
while(a == b && flag++ < 1000) {
if(this_returns_true()) {
flag = 10000;
continue;
}
/*The code here may not be executed*/
}
Using a boolean flag it would be...
while(a == b && flag == true) {
if(this_returns_true()) {
flag = false;
continue;
}
/*The code here may not be executed*/
}

Answer 2

Just change the while to if. There's no need for a loop if you only want to execute something once.

Answer 3

You can use break; with an if statement inside the while loop. So that if a condition is true you will break out from the while loop.
Example
if (operation != "e")
break;
If you're not allowed to use break, I suggest you don't use a loop. And just calculate it once.

Answer 4

I am not very experienced with C++ but I think you mean the break; statement
https://msdn.microsoft.com/library/37zc9d2w.aspx

Answer 5

Use
break;
This will end the loop each time. You can wrap an if statement around it to apply conditions for exiting.

Answer 6

If you have to use the while loop just add break; and that will break out of the loop. If you don't have to I would change that to an if statement. Example: if(varName == '+'){
Num1 + num2;}
Sorry for format, on mobile

Answer 7

The code block:
cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
while (operation == "e" || operation == "E")
{
cout << "Operation type invalid." << endl;
cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
}
Doesn't do what you're promising the user:
Please enter what operation you'd like to perform or e/E to end program:
If "e" or "E" is entered, the loop won't stop and ask for input again.
You probably want to have something like this:
do {
cin >> operation;
while (operation == "+" || operation == "-" || operation == "*" || operation == "/") {
// ...
}
} while(operation != "e" && operation != "E");
As for your silly restrictions not to use do {} while(); (kick your professor in the ass, do twice at least):
cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
while(operation != "e" && operation != "E") {
if (operation == "+" || operation == "-" || operation == "*" || operation == "/") {
// ...
}
else {
cout << "Operation type invalid." << endl;
cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
}
}

Answer 8

I guess that what you are actually trying to achieve is this.
The first loop should be refactored (ie: loop until operation is nether 'e' nor 'E'), the second loop should be an if-else-statement (checking whether the operation is valid).
int main()
{
int numOne;
int numTwo;
int result;
string operation;
cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
while (operation != "e" && operation != "E") {
if (operation == "+" || operation == "-" || operation == "*" || operation == "/") {
// your valid operation code...
} else {
cout << "Operation type invalid." << endl;
}
cout << "Please enter what operation you'd like to perform or e/E to end program: ";
cin >> operation;
}
return 0;
}