Logical Operators in Solidity

Logical Operators are used to combining two or more conditions. Solidity has the following types of logical operators:

1. Logical AND: Logical AND takes two operands and gives the valid Boolean result. The logical AND operator evaluates to true when all the operands are true (non-zero) otherwise false(zero). It is denoted by &&.
2. Logical OR: Logical OR takes two operands and gives the valid Boolean result. The logical OR operator evaluates to true when at least one of the operands is true (non-zero) or otherwise false(zero). It is denoted by ||.
3. Logical NOT: Logical NOT takes one operand and gives its complement as the result. The logical NOT operator evaluates to true (non-zero) if the operand is false (zero) and vice-versa. It is denoted by !.

Operation	Denotation	Description
Logical AND	&&	It evaluates to true when all the operands are true (non-zero) otherwise false (zero)
Logical OR	||	It evaluates to true when at least one of the operands is true (non-zero) otherwise false (zero)
Logical NOT	!	It evaluates to true (non-zero) if the operand is false (zero) and vice-versa

These logical operators are used to evaluate conditions in different situations.

Below is the Solidity program to implement the Logical Operators:

Solidity

// Solidity program to implement
// the Logical Operators
pragma solidity ^0.5.0;

contract logical {

  function logicaloperator (bool a , bool b) public pure returns (bool, bool, bool) {
    // Logical AND
    bool logicaland = a && b;

    // Logical OR
    bool logicalor = a || b;

    // Logical NOT
    bool logicalnot = !b;

    return (logicaland, logicalor, logicalnot);
  }
}

Output: Let us have two Boolean variables a and b.

Case 1: When a is true and b is false.

Case 2: When a is false and b is false.

Case 3: When a is true and b is true.

Case 4: When a is false and b is true.