C++ ceil()

#include <iostream>
#include <cmath>
using namespace std;

int main() {
  
  // find the smallest possible integer value >= 15.08   
  cout << ceil(15.08);

  return 0;
}

// Output: 16

ceil() Syntax

The syntax of the ceil() function is:

ceil(double num);

ceil() Parameters

The ceil() function takes the following parameter:

• num - floating-point number whose ceiling value is to be computed

ceil() Return Value

The ceil() function returns:

• the smallest possible integer value which is greater than or equal to num

ceil() Prototypes

The prototypes for ceil() as defined in the cmath header file are:

double ceil(double num);

float ceil(float num);

long double ceil(long double num);

// for integral types
double ceil(T num);

Example 1: C++ ceil()

#include <iostream>
#include <cmath>
using namespace std;

int main() {
  double num = 10.25;

  double result = ceil(num);

  cout << "Ceil of " << num << " = " << result;

  return 0;
}

Output

Ceil of 10.25 = 11

Example 2: C++ ceil() for Integral Types

#include <iostream>
#include <cmath>
using namespace std;

int main() {
  int num = 15;

  double result = ceil(num);

  cout << "Ceil of " << num<< " = " << result;

  return 0;
}

Output

Ceil of 15 = 15

We will always get the same result for integral types. So this function is not used with integral types in practice.