Assignment operators
- Dart course
- Beginner
- Lesson 25/116
- 4 min
Learn shortcut assignments with =, +=, -= and ++/--.
Assignment operators
The basic assignment operator is =: x = 5;. Besides it, compound assignment operators provide shortcuts.
x += 5 actually means x = x + 5. Similarly there are -=, *=, /=, %=. They make code shorter and clearer.
++ and -- increase or decrease by one: x++ is the same as x = x + 1. They are common in loops.
Practice Compound assignment
Start with var x = 10;. Do x += 5; and print print(x). Then do x++; and print print(x) again.
Starter code
// Use compound assignmentSample solution
void main() {
var x = 10;
x += 5;
print(x);
x++;
print(x);
}Expected output
15 16
Increment and decrement
++ increases a variable by 1; -- decreases it by 1. x++ is the same as x = x + 1; x-- is the same as x = x - 1.
There are prefix and postfix forms: ++x (prefix) increments then returns; x++ (postfix) returns then increments. Used alone they are the same.
In loops i++ is common: for (var i = 0; i < 5; i++). This advances the counter by one each time.
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does x += 5 do?
- Multiplies x by 5
- Sets x to 5
- Throws an error
- Adds 5 to x (x = x + 5) Correct answer
Explanation: += is a shortcut for x = x + 5.
2 Compound assignment sign
x ____= 3; // x = x + 3x += 3; // x = x + 3Explanation: It is part of the += sign.
3 Assignment operators
| Term | Meaning |
|---|---|
= |
Assignment |
+= |
Add and assign |
++ |
Increment |
-- |
Decrement |