Equality Operators: == and !=

The latest version of this topic can be found at Equality Operators: == and !=.

Syntax

  
      expression == expression  
expression != expression  

Remarks

The binary equality operators compare their operands for strict equality or inequality.

The equality operators, equal to (==) and not equal to (!=), have lower precedence than the relational operators, but they behave similarly. The result type for these operators is bool.

The equal-to operator (==) returns true (1) if both operands have the same value; otherwise, it returns false (0). The not-equal-to operator (!=) returns true if the operands do not have the same value; otherwise, it returns false.

Operator Keyword for !=

The not_eq operator is the text equivalent of !=. There are two ways to access the not_eq operator in your programs: include the header file iso646.h, or compile with the /Za (Disable language extensions) compiler option.

Example

// expre_Equality_Operators.cpp  
// compile with: /EHsc  
#include <iostream>  
  
using namespace std;  
  
int main() {  
   cout  << boolalpha  
         << "The true expression 3 != 2 yields: "  
         << (3 != 2) << endl  
         << "The false expression 20 == 10 yields: "  
         << (20 == 10) << endl;  
}  

Equality operators can compare pointers to members of the same type. In such a comparison, pointer-to-member conversions, as discussed in Pointer-to-Member Conversions are performed. Pointers to members can also be compared to a constant expression that evaluates to 0.

See Also

Expressions with Binary Operators
C++ Operators
C++ Built-in Operators, Precedence and Associativity
C Relational and Equality Operators