trunc()

The trunc() function rounds the specified argument towards zero and returns the nearest integral value not larger in magnitude than the argument.

std::trunc(x);

The x parameter is the value to be truncated.

The data type of the return value can be double, float, or long double.

#include <iostream>
#include <cmath>

int main() {
  double x = -3.14159;
  double result;

  result = std::trunc(x);

  std::cout << "trunc(" << x << ") = " << result << "\n";
}

This will produce the following output:

trunc(-3.14159) = -3

The following example uses the trunc() function to round 12.3456 towards zero returning the value 12:

Code
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