add: slice internals exercises

16-slices/exercises/19-observe-len-cap/solution/main.go

@@ -0,0 +1,76 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import "fmt"
+
+func main() {
+	// --- #1 ---
+	// var games []string
+	// fmt.Printf("games's len    : %d cap: %d\n", len(games), cap(games))
+
+	// games := []string{}
+	// fmt.Printf("games's len    : %d cap: %d\n", len(games), cap(games))
+
+	// games = append(games, "pacman", "mario", "tetris", "doom")
+	// fmt.Printf("games's len    : %d cap: %d\n", len(games), cap(games))
+
+	games := []string{"pacman", "mario", "tetris", "doom"}
+	fmt.Printf("games's len    : %d cap: %d\n", len(games), cap(games))
+
+	// --- #2 ---
+	fmt.Println()
+
+	for i := 0; i <= len(games); i++ {
+		s := games[:i]
+		fmt.Printf("games[:%d]'s len: %d cap: %d\n", i, len(s), cap(s))
+	}
+
+	// --- #3 ---
+	fmt.Println()
+
+	zero := games[:0]
+	fmt.Printf("games's     len: %d cap: %d\n", len(games), cap(games))
+	fmt.Printf("zero's      len: %d cap: %d\n", len(zero), cap(zero))
+
+	for _, v := range []string{"ultima", "dagger", "pong", "coldspot", "zetra"} {
+		zero = append(zero, v)
+		fmt.Printf("zero's      len: %d cap: %d\n", len(zero), cap(zero))
+	}
+
+	// --- #4 ---
+	fmt.Println()
+
+	for n := range zero {
+		s := zero[:n]
+		fmt.Printf("zero[:%d]'s  len: %d cap: %d\n", n, len(s), cap(s))
+	}
+
+	// --- #5 ---
+	fmt.Println()
+
+	zero = zero[:cap(zero)]
+	for n := range zero {
+		s := zero[:n]
+		fmt.Printf("zero[:%d]'s  len: %d cap: %d - %q\n", n, len(s), cap(s), s)
+	}
+
+	// --- #6 ---
+	fmt.Println()
+
+	zero[0] = "command & conquer"
+	games[0] = "red alert"
+	fmt.Printf("zero  : %q\n", zero)
+	fmt.Printf("games : %q\n", games)
+
+	// --- #7 ---
+	// uncomment and see the error.
+	// _ = games[:cap(games)+1]
+	// or:
+	// _ = games[:5]
+}