Parameters and return

Learn to write functions with parameters and return values.

Parameters and return values

Parameters are always passed by copying (pass by value): changing a parameter inside the function doesn't affect the caller's variable.

func artir(n int) {
    n++
}

x := 5
artir(x)
fmt.Println(x)  // 5, unchanged

To have the change reach the caller, either return the new value or pass a pointer (you'll see this later).

The signature

A function's parameter and return types are its signature. Consecutive parameters of the same type are shortened: func alan(en, boy float64) float64. For an unused parameter, _ can be written instead of a name. Go has no default parameter values; every argument is given explicitly.

Exercise Rectangle area

Write the alan(en, boy float64) float64 function and print the result of alan(3, 4.5).

Show example solution

package main

import "fmt"

func alan(en, boy float64) float64 {
    return en * boy
}

func main() {
    fmt.Println(alan(3, 4.5))
}

Test yourself

After this call, what is <code>x</code>? <code>x := 5; x = ikiKat(x)</code> (ikiKat returns n*2)
- 10
- 5
- 0
- 25
Show answer

10 — The function works on a copy but returns the result; assigning it to x makes x 10.

Shortened parameters

func alan(en, boy ____) float64 {
    return en * boy
}

Show answer

func alan(en, boy float64) float64 {
    return en * boy
}

Concept

Pass by value

A copy is taken
Signature

Parameter + return types
_ parametresi

An unused value
Default value

Not in Go

Next lesson: Multiple return

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