Overview
Comparison operators (also called relational operators) are used to compare two values. They always return a boolean value: true or false.
Comparison Operators Table
| Operator | Description | Example | Result |
|---|
== | Equal to | 18 == 18 | true |
!= | Not equal to | 18 != 18 | false |
> | Greater than | 18 > 17 | true |
< | Less than | 18 < 18 | false |
>= | Greater than or equal to | 18 >= 18 | true |
<= | Less than or equal to | 18 <= 18 | true |
Basic Example
Here’s a complete example demonstrating all comparison operators:
void main() {
int edad = 18;
print(edad == 18); // Igual: true
print(edad != 18); // Diferente: false
print(edad > 17); // Mayor que: true
print(edad < 18); // Menor que: false
print(edad >= 18); // Mayor o igual: true
print(edad <= 18); // Menor o igual: true
}
true
false
true
false
true
true
Comparison operators are essential for control flow statements like if, while, and for loops.
Understanding Equality
Equal (==) vs Not Equal (!=)
int x = 5;
int y = 10;
print(x == y); // false (5 is not equal to 10)
print(x != y); // true (5 is different from 10)
In Dart, use == for equality comparison, not =. The single = is the assignment operator!
x == 5 checks if x equals 5x = 5 assigns 5 to x
Range Comparisons
Greater Than and Less Than
int score = 85;
print(score > 90); // false
print(score > 80); // true
print(score < 100); // true
print(score < 85); // false
Inclusive Comparisons
The >= and <= operators include the boundary value:
int age = 18;
print(age >= 18); // true (18 is included)
print(age > 18); // false (must be greater, not equal)
print(age <= 18); // true (18 is included)
print(age < 18); // false (must be less, not equal)
Use >= and <= when you want to include the boundary value in your comparison. For example, “age must be 18 or older” would use age >= 18.
Practical Examples
Age Verification
int userAge = 20;
bool isAdult = userAge >= 18;
print(isAdult); // Output: true
Password Length Check
String password = "mypass123";
bool isValidLength = password.length >= 8;
print(isValidLength); // Output: true
Grade Evaluation
int grade = 75;
bool passed = grade >= 60;
bool excellence = grade >= 90;
print('Passed: $passed'); // Output: Passed: true
print('Excellence: $excellence'); // Output: Excellence: false
Range Checking
int temperature = 22;
bool isComfortable = temperature >= 18 && temperature <= 25;
print(isComfortable); // Output: true