C++ Relational Operators

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Relational Operators

In C++, relational operators are used to compare values or expressions. These check the relationship between the operands and return a result in a boolean (true or false).

These comparisons are based on conditions like equality, inequality, greater than, less than, etc.

Relational operators are a fundamental part of a programming language as they help in decision-making, loops, and conditional checks.

List of Relational Operators

This is the following list of the relational operators in C++ −

• Equal to (==) − It checks if two values are equal.
• Not equal to (!=) − It checks if two values are not equal.
• Greater than (>) − It checks if the left operand is greater than the right.
• Less than (<) − It checks if the left operand is less than the right.
• Greater than or equal to (>=) − It checks if the left operand is greater than or equal to the right.
• Less than or equal to (<=) − It checks if the left operand is less than or equal to the right.

Relational Operators Usage

Relational operators are used to compare two values or objects in C++. Here we will see the list of following, where relational operators can be used.

• Comparing Integers − It can be used for comparing integer data types like int, long, short, etc.
• Comparing Floating-Point Numbers − Relational operators can also be used to compare floating-point numbers (float, double, etc.). However, due to precision issues with floating-point arithmetic, the results may not always be as expected when dealing with very small or very large numbers.
• Comparing Characters and Strings − Relational operators compare characters based on their ASCII values. Strings are objects of the std::string class, and relational operators are overloaded to compare them lexicographically (in alphabetical order).
• Comparing Objects (Custom Classes) − In C++, you can overload relational operators for custom objects, allowing you to compare instances of a class based on certain criteria.

Example of Relational Operators

The following is an example of relational operators:

#include <iostream>
#include <cmath>  // For floating-point comparison
#include <string> 

using namespace std;

// Custom class to overload relational operators
class Point {
   public:
      int x, y;
      Point(int x, int y) : x(x), y(y) {}

   bool operator>(const Point& p) { return (x*x + y*y) > (p.x*p.x + p.y*p.y); }
   bool operator==(const Point& p) { return (x == p.x && y == p.y); }
};

int main() {

   // Comparing Integers
   int a = 5, b = 10;
   cout << (a > b) << " " << (a == b) << endl; 

   // Comparing Floating-Point Numbers
   double x = 5.0, y = 5.0000001;
   cout << (fabs(x - y) < 1e-6) << endl; 

   // Comparing Characters
   char c1 = 'A', c2 = 'B';
   cout << (c1 < c2) << " " << (c1 == c2) << endl; 

   // Comparing Strings
   string str1 = "apple", str2 = "banana";
   cout << (str1 < str2) << " " << (str1 == str2) << endl; 

   // Comparing Objects
   Point p1(3, 4), p2(5, 12);
   cout << (p1 > p2) << " " << (p1 == p2) << endl;

   return 0;
}

Output

0 0
1
1 0
1 0
0 0

Relational Operators and Conditional Statements

In C++, Relational Operators in conditional statements help the program with decision-making and give results (true or false) based on the result of the comparison.

Syntax for if-else with Relational Operators

Here we will see the syntax for if-else with relational operators.

if (a > b) {

   // a is greater than b
   
} else if (a == b) {

   // a is equal to b
   
} else {

   // a is less than b
   
}

Syntax for while Loop with Relational Operators

Here we will see the syntax for while loop with relational operators.

int i = 1;
while (i <= 5) {
   if (i < 5) {
   
      // i is less than 5
	  
   } else if (i == 5) {
   
      // i is equal to 5
	  
   }
   i++;
}

Relational Operators with Logical Operators

In C++, relational operators (>, <, ==, !=, >=, <=) can be combined with logical operators (&&, ||, !) to form complex expressions, which allow for more advanced decision-making. this is helpful when you need to check multiple conditions in one expression.

Example

#include <iostream>
using namespace std;

int main() {
   int age = 25, height = 180;

   // Check if age is between 18 and 30 and height is greater than 170
   if (age >= 18 && age <= 30 && height > 170)
   cout << "The person qualifies!" << endl;

   // Check if age is outside 18-30 or height is <= 170
   if (age < 18 || age > 30 || height <= 170)
   cout << "The person does not qualify!" << endl;

   // Check if age is NOT between 18 and 30 or height is NOT > 170
   if (!(age >= 18 && age <= 30) || !(height > 170))
   cout << "The person does not qualify due to NOT condition!" << endl;

   return 0;
}

Output

The person qualifies!

Limitations of Relational Operators

• Precision issues with floating-point comparisons (e.g., float or double types may not behave as expected due to rounding errors).
• Comparing non-numeric types (e.g., comparing objects, strings, or custom classes might need custom operator overloads).
• Ambiguities in complex expressions where the order of evaluation or operator precedence can lead to unintended results.
• Type coercion when using relational operators with mixed data types (e.g., comparing int and double).