Why the second version didn't work ?

[MohammadAlshareef]

I made a program that put letter between numbers which you enter ...
I made two version of this code but the second code didn't work although that I just made one more variable and put it instead of (num % dev) as the following code

The first version:

  #include <iostream>
#include <cmath>
using namespace std;
int main () {
long long num,dev,devv;
char letter;
dev = 10;
devv = 1;
cin >> num;
cin >> letter;
while (num % dev != num ) {
        dev *= 10;
        devv *= 10;

}
while (dev != 10){
    cout << num % dev / devv << letter;
    dev /= 10;
    devv /= 10;
}
if (dev == 10){
    cout << num % dev;
}

return 0;
}

The second version :

#include <iostream>
#include <cmath>
using namespace std;
int main () {
int num,dev,devv,result,result2;
char letter;
dev = 10;
devv = 1;
cin >> num;
cin >> letter;
result = num % dev;
result2 = num % dev / devv;
while (result != num ) {
        dev *= 10;
        devv *= 10;

}
while (dev != 10){
    cout << result2 << letter;
    dev /= 10;
    devv /= 10;
}
if (dev == 10){
    cout << result;
}

return 0;
}
}

[dhayden]

while (num % dev != num ) {
        dev *= 10;
        devv *= 10;
}

Since dev changes each time through the loop, the value of num%dev changes also.

result = num % dev;
result2 = num % dev / devv;
while (result != num ) {
        dev *= 10;
        devv *= 10;
}

Here the value of result is set before entering the loop. So even though dev changes each time through the loop, result does not.

You may be thinking that C++ variables are like cells in a spreadsheet. In a spreadsheet you can assign a formula to a cell and when anything in the formula changes, the value of the cell with the formula changes too. C++ isn't like that. Variables contain values that are set when you assign something to them. The value remains unchanged until the program changes the variable itself.

Hope this helps,
Dave

[MohammadAlshareef]

To be honest i didn't understand you well in the last to lines you wrote ! and what should i do to make "result" variable changes ?
And thank you anyways ^_^

[Ganado]

and what should i do to make "result" variable changes ?

Assign an up-to-date value for it, before you print it on line 24.

The only time you currently assign to result is on line 11, result = num % dev;
result will still have the value assigned to it on line 11 when you print it on line 24, unless you assign something else to it.

Unlike a math variable, a C++ int variable cannot be "symbolic". It can only hold a number, like 432. It can't contain an entire math expression.

[MohammadAlshareef]

So the variable will not change unless i change my self ?

[dhayden]

So the variable will not change unless i change my self ?

Exactly. When the program executes a statement like result = num % dev, it evaluates the expression on the right side using the values of the variables (num and dev) as they exist at that time. The result of the evaluation is a number. This number gets stored in the variable result. The number remains unchanged until you assign a new value to result.

So even if num and dev change, the value of result remains the same.

[MohammadAlshareef]

Thank you very much ,You and Ganado ^_^