Why pow(10,5) = 9,999 in C++

Question

Recently i write a block of code:

const int sections = 10;

for(int t= 0; t < 5; t++){
   int i = pow(sections, 5- t -1);  
   cout << i << endl;
}

And the result is wrong:

9999
1000
99
10
1

If i using just this code:

for(int t = 0; t < 5; t++){
    cout << pow(sections,5-t-1) << endl; 
}

The problem doesn't occur anymore:

10000
1000
100
10
1

Does anyone give me an explaination? thanks you very much!

Answer 1

Due to the representation of floating point values pow(10.0, 5) could be 9999.9999999 or something like this. When you assign that to an integer that got truncated.

EDIT: In case of cout << pow(10.0, 5); it looks like the output is rounded, but I don't have any supporting document right now confirming that.

EDIT 2: The comment made by BoBTFish and this question confirms that when pow(10.0, 5) is used directly in cout that is getting rounded.