Logical Operators

Learn how to combine and manipulate boolean values using logical operators in Dart

Overview

Logical operators are used to combine or invert boolean values. They are essential for creating complex conditions in your programs.

Logical Operators Table

Operator	Name	Description	Example
&&	AND	Returns true if both operands are true	true && false → false
`		`	OR	Returns true if at least one operand is true	`true		false→true`
!	NOT	Inverts the boolean value	!true → false

Basic Example

Here’s a complete example demonstrating logical operators:

void main() {
  bool esEstudiante = true;
  bool tieneTitulo = false;
  int valor = 28;

  print(valor == 18 || tieneTitulo);
  print(esEstudiante && tieneTitulo);  // AND: false
  //print(esEstudiante || tieneTitulo);  // OR: true
  print(!esEstudiante);                // NOT: false

  /*
  Tabla de verdad AND:
  true  && true   = true
  true  && false  = false
  false && true   = false
  false && false  = false
  */
}

Output:

false
false
false

AND Operator (&&)

The AND operator returns true only when both conditions are true.

Truth Table for AND

Left	Right	Result
true	true	true
true	false	false
false	true	false
false	false	false

Example

bool hasLicense = true;
bool hasInsurance = true;
bool canDrive = hasLicense && hasInsurance;
print(canDrive);  // Output: true

The AND operator uses “short-circuit” evaluation: if the left operand is false, the right operand is not evaluated because the result will always be false.

OR Operator (||)

The OR operator returns true when at least one condition is true.

Truth Table for OR

Left	Right	Result
true	true	true
true	false	true
false	true	true
false	false	false

Example

bool isWeekend = false;
bool isHoliday = true;
bool canRelax = isWeekend || isHoliday;
print(canRelax);  // Output: true

The OR operator also uses “short-circuit” evaluation: if the left operand is true, the right operand is not evaluated because the result will always be true.

NOT Operator (!)

The NOT operator inverts a boolean value.

Truth Table for NOT

Value	Result
true	false
false	true

Example

bool isLoggedIn = true;
bool isGuest = !isLoggedIn;
print(isGuest);  // Output: false

The NOT operator is useful for checking the opposite of a condition. For example, !isEmpty is more readable than isEmpty == false.

Combining Logical Operators

You can combine multiple logical operators to create complex conditions:

int age = 25;
bool hasTicket = true;
bool isStudent = false;

// Must be 18 or older AND have a ticket OR be a student
bool canEnter = (age >= 18 && hasTicket) || isStudent;
print(canEnter);  // Output: true

Practical Examples

Access Control

bool isAdmin = false;
bool isOwner = true;
bool canDelete = isAdmin || isOwner;
print(canDelete);  // Output: true

Form Validation

String username = "john";
String password = "pass1234";

bool validUsername = username.length >= 3;
bool validPassword = password.length >= 8;
bool canSubmit = validUsername && validPassword;

print(canSubmit);  // Output: true

Eligibility Check

int age = 16;
bool hasParentalConsent = true;

bool canParticipate = age >= 18 || (age >= 13 && hasParentalConsent);
print(canParticipate);  // Output: true

Inverted Conditions

bool isProcessing = false;
bool canStart = !isProcessing;
print(canStart);  // Output: true