Trying to self-teach, need guidance

[blake]

So I'm thinking about going back to school and pursing a degree in CS. Figured before I dove right in that I'd try to teach myself C++ and see how it goes, but I've already ran into an issue. I'm using the Dummies guide to C++ and with Code::Blocks IDE. For some reason I cannot get this code to output correctly, its a for a loop and I typed it exactly the way it is in the book but it prints 50050 to the console. Here's the code:

#include <iostream>

using namespace std;

int main()
{
double x = 0.0;
double i;

for(i = 0.0; i <= 100.0; i += 0.1)
{
x += i;
}

cout << x << endl;

return 0;

}

I thought maybe I just had something in the IDE incorrectly configured or something, any help would be much appreciated.

[Moschops]

Computer Science is not programming, but that's for someone else here to talk about.

What value were you expect in this program? The first issue I see is that you're trying to compare floating point numbers. This is fundamentally flawed http://floating-point-gui.de/

[blake]

The book made it sound like it was a counter. I had assumed it would count to 100 in increments of 0.1.

[Moooce]

it does, but notice that the code outputs the value of x, not i.

[iN6qM4Gy]

Just make it so the code outputs i instead of outputting x inside the for loop. really x isn't even needed in this program. to make the code even shorter write it like this:

#include <iostream>

using namespace std;

int main()
{
for(double i = 0.0; i <= 100.0; i += 0.1)
{
cout << i << endl;
}


return 0;

}

[slider57]

if you notice in your code you have: x += i;
This is saying in more simple terms: x = x + i;
i increments in 0.1 increments. So if you replace the variables with actual numbers (and assuming x = 0, you should always initialize your variables so you know what is in them at the start)
you get for the first few cases:

0 = 0 + 0.1 = 0.1; 1st case
0.1 = 0.1 + 0.2 = 0.3; 2nd case
0.3 = 0.3 + 0.4 = 0.7; 3rd case
0.7 = 0.7 + 0.5 = 1.2; 4th case
and so on and so forth. To do a count with the for loop there are a couple different ways to do it. First, in your code in the for loop you have:

for (i = 0.0; i <= 100; i+= .1) // this wont give you a count
// instead try this
for (i = 0.0; i <= 100; i) // this keeps i from incrementing allowing x to increment correctly 

or you can use the code as Yumixfan gives you and just output i, but you want to modify it a little

[blake]

Thanks guys I got it working. I'm sure I'll have many more questions as I voyage through the world of programming. I'll probably be on here a lot, maybe not posting but at least searching through old post for some answers.