Add and subtract

Add and test the addition and subtraction functions.

The add and subtract functions

The first two functions of the calculator are add and subtract. Both take two Ints and return an Int. add computes a + b; subtract computes a - b.

fun add(a: Int, b: Int): Int {
    return a + b
}

fun subtract(a: Int, b: Int): Int {
    return a - b
}

You can call these from main as add(5, 3) and subtract(5, 3).

Exercise Add add and subtract

Above the existing main, add fun add(a: Int, b: Int): Int { return a + b } and fun subtract(a: Int, b: Int): Int { return a - b }. Inside main, add println(add(5, 3)) and println(subtract(5, 3)); keep the existing println.

Show example solution

fun add(a: Int, b: Int): Int {
    return a + b
}
fun subtract(a: Int, b: Int): Int {
    return a - b
}
fun main() {
    println("Calculator")
    println(add(5, 3))
    println(subtract(5, 3))
}

When to use a function?

If you'll perform the same calculation in several places, it's good to move it into a function. In the calculator, add(5, 3) and add(10, 20) share code; this reduces errors and improves readability.

Functions also make testing easier by breaking code into pieces. Putting each operation in its own function simplifies debugging in the calculator.

Test yourself

Match the concepts

fun

Function
Int

Integer
return

Return
println

Output
What does `add(5, 3)` return?
- It throws an error
- 2
- 15
- 8
Show answer

8 — The add function sums two numbers.

Complete the return statement

fun subtract(a: Int, b: Int): Int {
    return a ____ b
}

Show answer

fun subtract(a: Int, b: Int): Int {
    return a - b
}

Next lesson: Multiply and divide

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