Return values

Learn to return a value from a function with return.

Return values

A function can return a value; you write the return keyword and a return type. Example: int add(int a, int b) { return a + b; }. This function takes two integers and returns their sum.

The return type tells what the function gives back: int, String, double, bool. When return is reached, the function ends; nothing after it runs.

The caller can store the returned value in a variable: var sum = add(3, 4);. The value 7 now lives in sum. Functions that give back nothing use void.

The return flow

A function stops as soon as it sees return. Lines after it do not run. Example: int first() { return 1; print('Never reached'); } — print is never executed.

You can write multiple returns; the first one reached decides the value. This is handy for conditional returns: if (x > 0) { return x; } return -x;.

void functions can also exit early with return;; in that case they return no value, they only end the function.

Exercise Compute the square

Define a square(int n) function that returns n * n. Add a print(square(5)) call inside main.

Show example solution

int square(int n) {
  return n * n;
}

void main() {
  print(square(5));
}

Test yourself

Match the return types

int

Integer
String

Text
double

Decimal
bool

Boolean
What happens after return?
- The next line also runs
- It throws
- A loop starts
- The function ends
Show answer

The function ends — return exits the function immediately.

The return expression

int add(int a, int b) {
  return ____;
}

Show answer

int add(int a, int b) {
  return a + b;
}

Next lesson: Arrow functions

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