add unassigned slice example (#475)

examples/slices/slices.go

@@ -9,11 +9,16 @@ func main() {
 
 	// Unlike arrays, slices are typed only by the
 	// elements they contain (not the number of elements).
+	// unassigned slice equal to nil and has a length of `0`
+	var s []string
+	fmt.Println("unassigned:", s, s == nil, len(s) == 0)
+
 	// To create an empty slice with non-zero length, use
 	// the builtin `make`. Here we make a slice of
 	// `string`s of length `3` (initially zero-valued).
-	s := make([]string, 3)
-	fmt.Println("emp:", s)
+	// `string`s of capacity `5`.
+	s = make([]string, 3, 5)
+	fmt.Println("emp:", s, "len:", len(s), "cap:", cap(s))
 
 	// We can set and get just like with arrays.
 	s[0] = "a"

examples/slices/slices.hash

@@ -1,2 +1,2 @@
-13835b88336e031808f2f3887cd43d0b9d85cad0
-76f4Jif5Z8o
+d255a550fe04d6a6d31c7256a1d980e675db0619
+ryiklDqjbId

examples/slices/slices.sh

@@ -1,7 +1,8 @@
 # Note that while slices are different types than arrays,
 # they are rendered similarly by `fmt.Println`.
 $ go run slices.go
-emp: [  ]
+unassigned: [] true true
+emp: [  ] len: 3 cap: 5
 set: [a b c]
 get: c
 len: 3