Simple C++ Error: "... undeclared (first use this function)"
<p>Hey guys, I am working on my first C++ program for school. For some reason I am getting the following error when I try to compile it:</p>

<pre><code>`truncate' undeclared (first use this function)
</code></pre>

<p>Full Source:</p>

<pre><code>#include &lt;iostream&gt;
#include &lt;math.h&gt;

using namespace std;

#define CENTIMETERS_IN_INCH 2.54
#define POUNDS_IN_KILOGRAM 2.2

int main() {
    double feet, inches, centimeters, weight_in_kg, weight_in_lbs;

    // get height in feet and inches
    cout &lt;&lt; "Enter height (feet): ";
    cin &gt;&gt; feet;
    cout &lt;&lt; "Enter (inches): ";
    cin &gt;&gt; inches;

    // convert feet and inches into centimeters
    centimeters = ((12 * feet) + inches) * CENTIMETERS_IN_INCH;

    // round 2 decimal places and truncate
    centimeters = truncate(centimeters);

    printf("Someone that is %g' %g\" would be %g cm tall", feet, inches, centimeters);

    // weights for bmi of 18.5
    weight_in_kg = truncate(18.5 * centimeters);
    weight_in_lbs = round(weight_in_kg * POUNDS_IN_KILOGRAM);

    printf("18.5 BMI would correspond to about %g kg or %g lbs", weight_in_kg,   weight_in_lbs);

    // weights for bmi of 25
    weight_in_kg = truncate(25 * centimeters);
    weight_in_lbs = round(weight_in_kg * POUNDS_IN_KILOGRAM);

    printf("25.0 BMI would correspond to about %g kg or %g lbs", weight_in_kg, weight_in_lbs);

    // pause output
    cin &gt;&gt; feet;

    return 0;
}

// round result
double round(double d) {
   return floor(d + 0.5);
}

// round and truncate to 1 decimal place
double truncate(double d) {
   return round(double * 10) / 10;
}
</code></pre>

<p>Any help would be appreciated. Thanks.</p>
