While loop failing with bool

[S36A7k9E]

For some reason, logical statement in the while loop will not change the bool value when I type in "Y" or "N". It just remains 1, or true, no matter what.

#include <iostream>
#include <string>

using namespace std;

int main(){

	// Declare variables and set some
	double GPA = 0;
	int CourseCount = 0;
	string CourseName = "Test";
	char Question;
	bool Choice;

	while (Choice = true) {
		// Ask for the Course name and store it for later use
		cout << "Please enter the course name: ";
		cin >> CourseName;

		cout << "Would you like to enter grades again?: ";
		cin >> Question;

		// Standardize the casing for this
		toupper(Question);

		if (Question = 'Y'){
			Choice = true;
		}
		else if (Question = 'N' ){
			Choice = !true;
		}
		else {
			cout << "\nERROR: Please enter a choice of Y/N.\n";
		} 

	} 

	return 0;
}

[keskiverto]

This Choice = true is an assignment. The variable Choice is set first, and then the value of Choice (true) is used in the conditional.

This Choice == true is a relational operator that returns true, if the value of Choice is equal to true.


PS. It is good practice to write true == Choice. If you accidentally forget the second equal sign, then the compiler will stop on impossible assignment.

[S36A7k9E]

Even so it's still not changing the value.

#include <iostream>
#include <string>

using namespace std;

int main(){

	// Declare variables and set some
	double GPA = 0;
	int CourseCount = 0;
	string CourseName = "Test";
	char Question;
	bool Choice = true;

	while (Choice == true) {
		// Ask for the Course name and store it for later use
		cout << "Please enter the course name: ";
		cin >> CourseName;

		cout << "Would you like to enter grades again?: ";
		cin >> Question;

		// Standardize the casing for this
		toupper(Question);

		if (Question = 'Y'){
			Choice = true;
		}
		else if (Question = 'N' ){
			Choice = !true;
		}
		else {
			cout << "\nERROR: Please enter a choice of Y/N.\n";
		} 

	} 

	return 0;
}

This still keeps looping through as if I never typed "n"

[MatthewRock]

!true is simply false :)

And you're doing the same error in all ifs; "=" is assignment; "==" is check. Line 26 and 29 are wrong.

[S36A7k9E]

Ah, that solved it gents. Thank you. I get so far and I forget the basics of operators.

[MatthewRock]

Just watch out for "=" and "==" :) For the beginners it may be hard to remember. If you want to make sure you won't make a mistake, you can do this trick(although, it does not always work):

//instead of...
if(question == 'Y')

//use:
if('Y' == question)

What's the difference, you may ask? Well, let's suppose, that you did what you just did:

//Your version:
if(question = 'Y') // Bug! You are assigning, where you wanted to compare; but your compiler won't tell you that
//It's a bug that may be tricky.

//Safer version:
if('Y' = question) // Compilation error! You are assigning a value to a constant, which isn't legal. 

In the second example, your compiler will show error, and you will notice your mistake.

Cheers!

[Nukem]

You might want to go with a do while in this situation...

#include <iostream>
#include <string>

using namespace std;

int main(){

	// Declare variables and set some
	double GPA = 0;
	int CourseCount = 0;
	string CourseName = "Test";
	char Question;
	bool Choice = true;

	do{
		// Ask for the Course name and store it for later use
		cout << "Please enter the course name: ";
		cin >> CourseName;

		cout << "Would you like to enter grades again? Y/N:  ";
		cin >> Question;
                }while(toupper(Question)=='Y');
        	
	} 

	return 0;
}