Array Programs

Learn array programs through an executable example, then connect the small demonstration to production code.

Arrays have fixed lengths as part of their types. This makes them useful for a known-size collection and for practicing indexed iteration.

The example finds a maximum without sorting or modifying the array, and handles the nonempty-array assumption explicitly.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import "fmt"

func main() {
	numbers := [5]int{7, 4, 12, 3, 9}
	max := numbers[0]
	for _, value := range numbers {
		if value > max {
			max = value
		}
	}
	fmt.Println("Maximum:", max)
	fmt.Println("Length:", len(numbers))
}

Output

Maximum: 12
Length: 5

Initialization starts max at the first element. The loop replaces it when 12 is encountered; length remains 5.

• An array length is part of its type: [3]int and [5]int are different types.
• Do not read index zero of an empty slice; check its length first.

Change the data and add minimum-value detection.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Array Programs in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.