Logical NOT Operator

Dart Logical NOT Operator takes a boolean value as operand (right side) and returns the result of logical NOT gate operation.

Logical NOT Operator returns true if the operand is false, or false if the operand is true. Therefore, logical NOT operator is used to check if the condition is not true.


! symbol is used for Logical NOT Operator.


The syntax for Logical OR Operator is

! operand

where operand is a boolean value or expression that evaluates to a boolean value.

Truth Table

The truth table of NOT operation is shown in the following.

operand! operand


Check if given number is not negative

In the following example, we check if the given integer number n is not negative. Let us first consider the condition of n being negative n < 0. And the condition to check if n is not negative would be !(n < 0), using logical NOT operator.


import 'dart:io';

void main(){
    print('Enter n');
    var n = int.parse(stdin.readLineSync()!);

    if ( !(n < 0) ) {
        print('$n is not negative.');
    } else {
        print('$n is negative.');


Enter n
58 is not negative.


Enter n
-25 is negative.


In this Dart Tutorial, we learned about Logical NOT Operator, its syntax and usage, with examples.