Round in STL C++

February 17, 2023

C++ STL Function : round()

On this page we will discuss about library function round() in STL which is used in C++. The cmath header file is a C++ standard library header file that contains a set of math functions and macro definitions that are used to perform mathematical operations. The round function in C++ is a function in the cmath library that rounds a number to the nearest integer.

Round in STL C++

Library Function round() in C++

In C++ programming language the round() function is included in cmath header file.

The round() function in C++ can be used to round any floating-point number within the range of the corresponding floating-point type (double, float, or long double) to the nearest integer. The value is rounded to the nearest integer, with half-integers being rounded to the nearest even integer.
For example, round(1.5) will return 2, while round(2.5) will return 2.

Syntax

double round(double x);
float round(float x);
long double round(long double x);

Parameters

The round() function takes a single parameter x.

ParameterDescription
xIt is a floating-point number which is to be rounded off.

Return value

The round() function in C++ returns the nearest integer to the floating-point number passed as an parameter as a double, float, or long double depending on the type of the function being called.

Function in C++

Static Members in C++

virtual in C++

Pointers in C++

References in C++

Implementation of round() function in C++

Example 1:

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

int main() {
    
  double num = 3.14;
  cout << "round(" << num  << ") = "<< round(num) << endl;  

  num = 3.7;
  cout << "round(" << num  << ") = "<< round(num) << endl; 

  return 0;
}

Output:

round(3.14) = 3
round(3.7) = 4

Example 2:

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

int main() {

  double num, result;

  num = -13.13;
  result = round(num);

  cout << "round(" << num << ") = " << result << endl;

  num = -15.48;
  result = round(num);

  cout << "round(" << num << ") = " << result << endl;
    
  num = -60.7;
  result = round(num);

  cout << "round(" << num << ") = " << result;
      
  return 0;
}

Output:

round(-13.13) = -13
round(-15.48) = -15
round(-60.7) = -61

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