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C++ ceil()

In this tutorial, we will learn about the C++ ceil() function with the help of examples.

The ceil() function in C++ returns the smallest possible integer value which is greater than or equal to the given argument.

It is defined in the cmath header file.

Example

#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.

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