Learn Go - Arrays and Slices Summary

arrays-slices.go

// Arrays and Slices
package main

import (
	"fmt"
)

func main() {
	// basic syntax and initialization
	grades := [3]int{97, 85, 93}
	grades2 := [...]int{96, 84, 92} // infers size
	fmt.Printf("Grades: %v\n", grades)
	fmt.Printf("Grades: %v\n", grades2)

	// Initialization and assignment
	var students [3]string
	fmt.Printf("Students: %v\n", students)
	students[0] = "Lisa"
	students[2] = "Arnold"
	fmt.Printf("Students: %v\n", students)
	fmt.Printf("Student: %v\n", students[2])
	students[1] = "Ahmed"
	fmt.Printf("Number of Student: %v\n", len(students))

	// Matrix (array of arrays)
	// var identityMatrix [3][3]int = [3][3]int{[3]int{1, 0, 0}, [3]int{0, 1, 0}, [3]int{0, 0, 1}}
	var identityMatrix [3][3]int
	identityMatrix[0] = [3]int{1, 0, 0}
	identityMatrix[1] = [3]int{0, 1, 0}
	identityMatrix[2] = [3]int{0, 0, 1}
	fmt.Println(identityMatrix)
	fmt.Println(identityMatrix[2][2])

	// Note, assigning a variable to an array creates a copy, not pointing to the same
	// you can assign the new variable the ADDRESS to have the new var point to the same values
	i2 := identityMatrix
	i3 := &identityMatrix
	identityMatrix[2][2] = 5
	fmt.Println(identityMatrix)
	fmt.Println(i2)
	fmt.Println(i3)

	// Slice, use nothing inside of the brackets (no elipses either)
	// Note, copies will automatically point to the original variable unlike arrays
	slice := []int{1, 2, 3}
	s2 := slice
	fmt.Println(slice)
	fmt.Printf("Length: %v\n", len(slice))
	fmt.Printf("Capacity: %v\n", cap(slice))
	fmt.Println(s2)
	slice[0] = 5
	fmt.Println(s2)
	fmt.Println(slice)

	// first number inclusive, second number exclusive
	// remember, slices all point to the same data
	a := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
	b := a[:]
	c := a[3:]
	d := a[:6]
	e := a[3:6]
	a[5] = 42
	fmt.Println(a)
	fmt.Println(b)
	fmt.Println(c)
	fmt.Println(d)
	fmt.Println(e)

	// use make to make slices
	f := make([]int, 3)
	fmt.Println(f)
	fmt.Printf("Length: %v\n", len(f))
	fmt.Printf("Capacity: %v\n", cap(f))
	g := make([]int, 3, 100)
	fmt.Println(f)
	fmt.Printf("Length: %v\n", len(g))
	fmt.Printf("Capacity: %v\n", cap(g))

	h := []int{}
	fmt.Println(h)
	fmt.Printf("Length: %v\n", len(h))
	fmt.Printf("Capacity: %v\n", cap(h))
	h = append(h, 1)
	fmt.Printf("Length: %v\n", len(h))
	fmt.Printf("Capacity: %v\n", cap(h))
	fmt.Println(h)
	h = append(h, 2, 3, 4, 5)
	fmt.Printf("Length: %v\n", len(h))
	fmt.Printf("Capacity: %v\n", cap(h))
	fmt.Println(h)

	// concatenate slices. ellipses spreads slice elements to individual arguments
	h = append(h, a...)
	fmt.Printf("Length: %v\n", len(h))
	fmt.Printf("Capacity: %v\n", cap(h))
	fmt.Println(h)
}