I cannot figure out why this while loop is endless [duplicate] - c++

Question

This question already has answers here:
Can anyone tell me why these functions are not giving me a result in a reasonable spectrum?
(2 answers)
Closed 9 years ago.
Here is the code I am currently working with:
bool playCraps(int currentGame, bool detailPrint, char isBetting, int startingBet)
{
bool crapsResult = NULL;
int currentGameStorage[100];
int currentRoll = 1;
int point = roll2Dice();
int printingNumber = 0;
currentGameStorage[0] = point;
if(point == 7 || point == 11)
{
crapsResult = true;
}
else if(point == 2 || point == 3 || point == 12)
{
crapsResult = false;
}
else
{
crapsResult = NULL;
}
while(crapsResult != true || crapsResult != false)
{
currentGameStorage[currentRoll] = roll2Dice();
if(currentGameStorage[currentRoll] == point)
{
crapsResult = true;
}
else if(currentGameStorage[currentRoll] == 7)
{
crapsResult = false;
}
currentRoll += 1;
}
currentRoll -= 1;
if(detailPrint == true)
{
cout << "Game " << currentGame << ": ";
for(printingNumber = 0; printingNumber <= currentRoll; printingNumber += 1)
{
cout << currentGameStorage[printingNumber] << " ";
}
if(crapsResult == true)
{
cout << "win";
}
else if(crapsResult == false)
{
cout << "lose";
}
cout << endl;
}
return crapsResult;
}
Whenever I run it it creates am emdless loop with no text appearing in the terminal. The function roll2Dice() simulates the roll of two six sided dice using the rand() function and adds the two results together. Any help would be appreciated.

Answer 1

Your while test, crapsResult != true || crapsResult != false is necessarily true, and therefore does not terminate. The crapsResult value is either true of false, which will make one of the two halves of the expression true, and one false. Both true || false and false || true evaluate to true.

Answer 2

As others have noted it's pretty obvious why the loop never ends.
Your use of NULL makes me think you wish you could have a bool which could hold three values (unset, true and false). You could achieve this with minimal changes by using a pointer to bool, but that's pretty disgusting. Enums are what you really need:
enum CrapsResult
{
unrolled,
true_result,
false_result
};
The pertinent code then becomes*:
CrapsResult crapsResult = unrolled;
int currentGameStorage[100];
int currentRoll = 1;
int point = roll2Dice();
int printingNumber = 0;
currentGameStorage[0] = point;
if(point == 7 || point == 11)
{
crapsResult = true_result;
}
else if(point == 2 || point == 3 || point == 12)
{
crapsResult = false_result;
}
else
{
crapsResult = unrolled;
}
while(crapsResult == unrolled)
{
currentGameStorage[currentRoll] = roll2Dice();
if(currentGameStorage[currentRoll] == point)
{
crapsResult = true_result;
}
else if(currentGameStorage[currentRoll] == 7)
{
crapsResult = false_result;
}
currentRoll += 1;
}
*I haven't actually compiled this.

Answer 3

while(crapsResult != true || crapsResult != false)
equals to
while(crapsResult == false || crapsResult == true)
.
//while(crapsResult == (false || true)) // Don´t matter
so as boolean has only false or true
it will always evaluate true and equals to this expression
while(true)

Answer 4

In C and C++, expressions can resolve to true or false based on the following: 0 is false, everything else is true. The formal definition of C's macros FALSE and TRUE is #define FALSE 0 and #define TRUE (!(FALSE)).
A variable of type bool can either be true or false. You initialize your crapsResult with the value of NULL. NULL is a macro defined as 0UL or 0ULL, which evaluates to false.
bool crapsResult = NULL;
is equivalent to
bool crapsResult = false;
So when your code does the following:
while (crapsResult != true || crapsResult != false)
one of these conditions is always met, so the loop always repeats.
You will need a second variable, presumably of type bool, to determine if you have an acceptable answer.
bool crapsResult = false;
bool haveCrapsResult = false;
int currentGameStorage[100];
int currentRoll = 1;
int point = roll2Dice();
int printingNumber = 0;
currentGameStorage[0] = point;
if(point == 7 || point == 11)
{
crapsResult = true;
haveCrapsResult = true;
}
else if(point == 2 || point == 3 || point == 12)
{
crapsResult = false;
haveCrapsResult = false;
}
while(!haveCrapsResult)
{
currentGameStorage[currentRoll] = roll2Dice();
if(currentGameStorage[currentRoll] == point)
{
crapsResult = true;
haveCrapsResult = true;
}
else if(currentGameStorage[currentRoll] == 7)
{
crapsResult = false;
haveCrapsResult = true;
}
currentRoll += 1;
}
currentRoll -= 1;
if(detailPrint == true)
{
cout << "Game " << currentGame << ": ";
for(printingNumber = 0; printingNumber <= currentRoll; printingNumber += 1)
{
cout << currentGameStorage[printingNumber] << " ";
}
if(crapsResult == true)
{
cout << "win";
}
else /*if(crapsResult == false) is redundant */
{
cout << "lose";
}
cout << endl;
}
return crapsResult;