Iterating over arrays in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the basic way to loop over an array in Go?

Use the for loop with range to get index and value for each element in the array.

beginner

What does the range keyword return when used with an array?

It returns two values: the current index and the value at that index in the array.

beginner

How can you ignore the index when iterating over an array in Go?

Use an underscore _ in place of the index variable to ignore it, like for _, value := range arr.

intermediate

Can you modify array elements while iterating with range in Go?

No, the value returned by range is a copy. To modify elements, use the index to access the array directly.

beginner

Write a simple Go code snippet to print all elements of an array of integers.

```go
package main

import "fmt"

func main() {
    arr := [3]int{10, 20, 30}
    for i, v := range arr {
        fmt.Printf("Index %d: Value %d\n", i, v)
    }
}
```

What does the range keyword return when used on an array in Go?

A Only the index of each element

B Only the value of each element

C Index and value of each element

D The entire array

range returns both the index and the value for each element when iterating over an array.

How do you ignore the index when using range to iterate over an array?

A Use <code>_</code> instead of the index variable

B Use <code>nil</code> instead of the index variable

C Use <code>0</code> instead of the index variable

D You cannot ignore the index

Using _ tells Go to ignore the index value.

Can you change the elements of an array by modifying the value variable inside a range loop?

A No, because the value is a copy

B Yes, it changes the original array

C Only if the array is a slice

D Only if you use pointers

The value variable is a copy, so modifying it does not change the original array element.

Which of these is the correct syntax to iterate over an array arr in Go?

A for (i, v) in arr {}

B for i in arr {}

C foreach arr as i, v {}

D for i, v := range arr {}

Go uses for i, v := range arr to iterate over arrays.

What happens if you omit the index variable in a range loop like for v := range arr?

A It will iterate only over the values

B It will cause a compile error

C It will iterate only over the indexes

D It will iterate over both index and value

You must specify both index and value or use _ to ignore one. Omitting the index variable causes a compile error.

Explain how to use a for range loop to iterate over an array in Go and print each element.

Think about how you get both index and value from the array.

Describe why modifying the value variable inside a range loop does not change the original array elements.

Consider how Go handles values when iterating.