A simple C++ While loop not working - c++

Question

I have a simple while loop i'm trying to implement but for the life of me can't figure out what I'm missing. I have currentuser initialized at the top to -1
while(currentuser = -1){
cout << "Enter user ID: ";
cin >> id;
currentuser = search(a, length, id);
}
My search function is this:
int search (User a[ ], int length, string userID){
User u;
string tempid;
int templegnth; //I ignore length for now as I will use it later
for(int i=0; i<50; i++){
tempid = a[i].getID();
templegnth = tempid.length();
if((tempid == userID)){
return i;
}
}
return -1;
}
I know its something very simple but the answer escapes me right now.

Answer 1

The = (assignment) operator is not the same as the == (equality) operator.
The line :
while(currentuser = -1){
first assigns -1 to currentuser, and then checks if currentuser has a non-zero value. This will always be the case (-1 != 0), so the loop will never end.
You likely meant this instead :
while(currentuser == -1){
which compares currentuser to -1, and continues the loop as long as that comparison is true.

Answer 2

You need to change:
while(currentuser = -1){
to be:
while(currentuser == -1){
Currently you are assigning currentuser to -1 every time your loop runs, rather than checking if it is still assigned to that value.

Answer 3

Try == -1 instead of = -1

Answer 4

You've got the answers but here is a tip on how to avoid it in the future.
Always try to use
while(-1 == currentuser){
std::cout << "Enter user ID: ";
std::cin >> id;
currentuser = search(a, length, id);
}
as this way
while(-1 = currentuser){
;
}
will be thrown out by the compiler

Answer 5

Even with the = changed to ==, the loop still has problems.
while(currentuser == -1){
std::cout << "Enter user ID: ";
std::cin >> id;
currentuser = search(a, length, id);
}
Typing an EOT (control-D on a Linux box, control-Z? on windows) will raise std::cin's end of file condition. The value of id won't be changed, and the lookup will presumably keep on returning -1. The result is an infinite loop with lots of spew to std::cout.
One way to fix this is to break out of the loop when the std::cin >> id; fails. For example, if (! (std::cin >> id)) break;

Answer 6

Whenever I use a while loop and a boolean, I try to make sure it only runs if it is above or is 50 but instead whenever I execute a cout with the while and int, the outcome is a literal mess, its like the while loop executes a lot more than it should. Eg.
int Buses;
int People;
cin >> People;
while(People >= 50){
Buses += 1;
People -= 50;
};
cout << Buses << endl;
and when I input 757, my result was 32782.
Even by subtracting the int value by 32767, the values sort of fix itself but not the higher numbers, 99 is 1, 101 is 2 but c++ says that 300 is 3 although it is meant to be 6.
(My solution I found: I had to declare the Person and Buses variable with a 0 because the value was different without the starting 0.)
This is the fixed code:
int Buses = 0;
int People = 0;
cin >> People;
while(People >= 50){
Buses += 1;
People -= 50;
};
cout << Buses << endl;