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
-//  to a slice, on each step of the loop. Observe the capacity.
+//  Write a program that appends elements to a slice
+//  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
-//     the capacity changes.
+//  4. Print the length and capacity of the slice "only"
+//     when its capacity changes.
 //
-//  5. Print also the growth rate by calculating the previous and
-//     the current capacity.
+//  BONUS: Print also the growth rate of the 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)
 	}
 }