help please

**comwizz2** · 08-02-2007

Hi im kinda new to C++ and im trying to write a program for a challenge site (osix.net), but i seem to be running into problems with my loop which wont even seem to run once...

Code:

#include <iostream>

using namespace std;

double Perm = 3;
int TimeTotal = 94;
int TimePass = 0;

int main()
{
    while (TimePass < TimeTotal)
    {
        Perm = Perm * (1+1/3);
        TimePass++;
    }

    cout << (int)Perm;
}

If i take out the line TimePass++; the loop works but doesn't end......
any help is appreciated!

**MacGyver** · 08-02-2007

Code:

Perm = Perm++;

We just had a discussion about this in the C forums. This is an undefined statement in C and in C++. The compiler may make this line of code do anything it wants.

Are you just trying to increment Perm by one? Then do this:

Code:

Perm++;

And for the future, turn your compiler's warnings up. It should have caught this.

**comwizz2** · 08-02-2007

Thnks i used to use c# for a while and that worked, but still my loop doesn't loop... doesn't even seem to run

**Daved** · 08-02-2007

Your loop is running 94 times as you want. The problem is that you are doing integer division and so you are multiplying by 1 every time, which doesn't change the value. The literals 1 and 3 are integers, so 1/3 is 0. To do floating point arithmetic, make them doubles by adding a decimal point. 1.0/3.0 is 0.33333.

**comwizz2** · 08-02-2007

Thanks

only problem is it spits out -2147483648!!!

**comwizz2** · 08-02-2007

I cannot get it to spit out a whole number all i get is scientific notation if i dont use int cast, but if i do use int cast, it gives me negative number

**Daved** · 08-02-2007

The number is too big to fit into an int, so it becomes negative. There are ways to not show scientific notation when displaying a double, look into the io manipulators from <iomanip>.

**hk_mp5kpdw** · 08-02-2007

Originally Posted by Daved

There are ways to not show scientific notation when displaying a double, look into the io manipulators from <iomanip>.

Yeah, something like this I think if memory serves:

Code:

#include <iomanip>

...

cout << fixed << Perm;

**brewbuck** · 08-02-2007

Originally Posted by comwizz2

I cannot get it to spit out a whole number all i get is scientific notation if i dont use int cast, but if i do use int cast, it gives me negative number

Code:

std::cout << std::fixed << Perm << std::endl;

**comwizz2** · 08-02-2007

Thanks everybody! after that final fix my program ran sucsessfully and i got the correct answer thanks very much

Thread: help please

Thread Tools

Search Thread

Display

help please