2022-12-18

chapter-3-composite-types/02_slices.go

@@ -13,4 +13,68 @@ func main() {
 
 	x = []int{1, 5: 4, 6, 10: 20, 11}
 	fmt.Println(x)
+	fmt.Println()
+
+	// access last element in a slice
+	fmt.Println(x[len(x)-1])
+	fmt.Println()
+
+	// empty slice is nil value (no type)
+	// can only compare slices to nil
+	var y []int
+	fmt.Println(y == nil)
+	fmt.Println()
+
+	// this notiation declares a nil slice
+	var y0 []int
+	fmt.Println("y0", y0 == nil)
+	// this notation declares an empty slice literal
+	var y1 = []int{}
+	fmt.Println("y1", y1 == nil)
+	// they are the same value ([]), but one is nil and one is not!
+	fmt.Println(y0, y1)
+	fmt.Println()
+
+	// can append more than one at a time
+	y = append(y, 1)
+	y = append(y, 2, 3)
+	fmt.Println(y)
+	fmt.Println()
+
+	// can use ... notation to unpack
+	x = append(x, y...)
+	fmt.Println(x)
+	fmt.Println()
+
+	// print the capacity of the slize (the memory reserved)
+	// show how it increases as you add more
+	var z []int
+	fmt.Println(z, len(z), cap(z))
+	z = append(z, 10)
+	fmt.Println(z, len(z), cap(z))
+	z = append(z, 20)
+	fmt.Println(z, len(z), cap(z))
+	z = append(z, 30)
+	fmt.Println(z, len(z), cap(z))
+	z = append(z, 40)
+	fmt.Println(z, len(z), cap(z))
+	z = append(z, 50)
+	fmt.Println(z, len(z), cap(z))
+	fmt.Println()
+
+	// make specifies type, length, capacity
+
+	// slice of ints length 5 (5 0's)
+	// don't use append with this as youll get [0,0,0,0,0,$append_val]
+	a := make([]int, 5)
+	fmt.Println(a)
+	fmt.Println()
+
+	// slice of ints length 0 capcity 10
+	b := make([]int, 0, 10)
+	fmt.Println(b)
+	// can use append with this
+	b = append(b, 1)
+	fmt.Println(b, len(b), cap(b))
+	fmt.Println()
 }