refactor: slice exercises 19-21

16-slices/exercises/20-observe-the-cap-growth/main.go

@@ -3,8 +3,9 @@ package main
 // ---------------------------------------------------------
 // EXERCISE: Observe the capacity growth
 //
-//  Write a program that loops 10 million times to append an element
+//  Write a program that appends elements to a slice
-//  to a slice, on each step of the loop. Observe the capacity.
+//  10 million times in a loop. Observe how the capacity of
+//  the slice changes.
 //
 //
 // STEPS
@@ -13,13 +14,12 @@ package main
 //
 //  2. Loop 10e6 times
 //
-//  3. On each loop step: Append an element to the slice
+//  3. On each iteration: Append an element to the slice
 //
-//  4. Only print the length and capacity of the slice everytime
+//  4. Print the length and capacity of the slice "only"
-//     the capacity changes.
+//     when its capacity changes.
 //
-//  5. Print also the growth rate by calculating the previous and
+//  BONUS: Print also the growth rate of the capacity.
-//     the current capacity.
 //
 //
 // EXPECTED OUTPUT

16-slices/exercises/20-observe-the-cap-growth/solution/main.go

@@ -15,15 +15,22 @@ func main() {
 		oldCap float64
 	)
 
+	// loop 10 million times
 	for len(nums) < 10e6 {
+		// get the capacity
 		c := float64(cap(nums))
 
+		// only print when the capacity changes
 		if c == 0 || c != oldCap {
+			// print also the growth ratio: c/oldCap
 			fmt.Printf("len:%-15d cap:%-15g growth:%-15.2f\n",
 				len(nums), c, c/oldCap)
 		}
+
+		// keep track of the previous capacity
 		oldCap = c
 
+		// append an arbitrary element to the slice
 		nums = append(nums, 1)
 	}
 }

16-slices/exercises/21-correct-the-lyric/main.go

@@ -8,30 +8,35 @@ import (
 // ---------------------------------------------------------
 // EXERCISE: Correct the lyric
 //
-//  You have a slice of lyrics data of Beatles' awesome
+//  You have a slice that contains the words of Beatles'
-//  song: Yesterday. Your goal is putting the words into
+//  legendary song: Yesterday. However, the order of the
-//  correct positions.
+//  words are incorrect.
 //
+// CURRENT OUTPUT
 //
-// STEPS
+//  [all my troubles seemed so far away oh i believe in yesterday now it looks as though they are here to stay]
-//
-//  1. Prepend "yesterday" to the `lyric` slice.
-//
-//  2. Put the words to the correct position in the `lyric` slice.
-//
-//  3. Print the `lyric` slice.
-//
 //
 // EXPECTED OUTPUT
 //
 //  [yesterday all my troubles seemed so far away now it looks as though they are here to stay oh i believe in yesterday]
 //
 //
+// STEPS
+//
+//  1. Prepend "yesterday" to the `lyric` slice.
+//
+//  2. Put the words to the correct positions in the `lyric` slice.
+//
+//  3. Print the `lyric` slice.
+//
+//     HINT: You don't need use the "yesterday" word from the `lyric` slice.
+//
+//
 // BONUS
 //
-//   . Think about when does the append allocates a new backing array.
+//   + Think about when does the append allocates a new backing array.
-//   . Then check whether your conclusions are true or not.
+//
-//   . You can use the prettyslice package to check the backing array.
+//   + Check whether your conclusions are correct.
 //
 // ---------------------------------------------------------
 

16-slices/exercises/21-correct-the-lyric/solution/main.go

@@ -17,7 +17,6 @@ func main() {
 	// yesterday all my troubles seemed so far away
 	// now it looks as though they are here to stay
 	// oh i believe in yesterday
-
 	lyric := strings.Fields(`all my troubles seemed so far away oh i believe in yesterday now it looks as though they are here to stay`)
 
 	// ------------------------------------------------------------------------
@@ -36,7 +35,7 @@ func main() {
 	lyric = append([]string{"yesterday"}, lyric...)
 
 	// ------------------------------------------------------------------------
-	// #2: Put the words to the correct position in the `lyric` slice.
+	// #2: Put the words to the correct positions in the `lyric` slice.
 	// ------------------------------------------------------------------------
 
 	//