C++ cmath floor() Function

The C++ cmath std::floor() function is used is used to round a given floating-point number x, down to the nearest integer and returns the largest integral value that is not greater than x.

This function is particularly useful in situations where you want to ensure that a value does not go above a certain limit, such as when dealing with indices in programming or setting boundaries in calculations.

Syntax

Following is the syntax for C++ cmath floor() function.

double floor(double x);
or
float floor(float x);
or
long double floor(long double x);

Parameters

• x - The floating-point number to be rounded down.

Return Value

The function returns the largest integer value that is less than or equal to the given number x.

Time Complexity

The time complexity of this function is constant, i.e.,O(1).

Example 1

The following example show's the basic usage of floor(), to round down the given floating-point number x.

#include <iostream>
#include <cmath>
int main() {
   double num = 5.7;
   double result = std::floor(num);
   std::cout << "The floor of " << num << " is: " << result << std::endl;
   return 0;
}

Output

Output of the above code is as follows

The floor of 5.7 is: 5

Example 2

The following example will demonstrate how the floor() function handles the negative value as a input.

#include <iostream>
#include <cmath>
int main() {
   double num = -3.4;
   double result = std::floor(num);
   std::cout << "The floor of " << num << " is: " << result << std::endl;
   return 0;
}

Output

Following is the output of the above code

The floor of -3.4 is: -4

Example 3

In this example, the input value 7.0 is a whole number. The floor() function returns 7, as it is already an integer. This demonstrates that floor() does not change values that are already whole numbers.

#include <iostream>
#include <cmath>
int main() {
   double num = 7.0;
   double result = std::floor(num);
   std::cout << "The floor of " << num << " is: " << result << std::endl;
   return 0;
}

Output

If we run the above code it will generate the following output

The floor of 7 is: 7