What is wrong with my For loops? i get warnings: comparison between signed and unsigned integer expressions [-Wsign-compare]
<pre><code>#include &lt;iostream&gt;
#include &lt;string&gt;
#include &lt;vector&gt;
#include &lt;sstream&gt;


using namespace std;

int main() {

    vector&lt;double&gt; vector_double;
    vector&lt;string&gt; vector_string;
    ...


    while (cin &gt;&gt; sample_string)
        {
            ...
        }

    for(int i = 0; i &lt;= vector_string.size(); i++)
        {
            ....
        }

    for (int i = 0; i &lt; vector_double.size(); i++)
        ....


    return 0;
}
</code></pre>
