refactor: slices 24th exercise

16-slices/exercises/24-fix-the-memory-leak/solution/api/api.go

@@ -7,15 +7,29 @@ import (
 )
 
 // DO NOT TOUCH THE FOLLOWING CODE
-// THIS IS THE API
-// YOU CANNOT CONTROL IT! :)
+// THIS IS THE IMAGINARY API CODE
+// YOU CANNOT CONTROL IT!
 
 // Read returns a huge slice (allocates ~65 MB of memory)
 func Read() []int {
+	// 2 << 22 means 2^(22 + 1)
+	// See this: https://en.wikipedia.org/wiki/Arithmetic_shift
+
+	// Perm function returns a slice with random integers in it.
+	// Here it returns a slice with random integers that contains
+	// 8,388,608 elements. One int value is 8 bytes.
+	// So: 8,388,608 * 8 = ~65MB
 	return rand.Perm(2 << 22)
 }
 
 // Report cleans the memory and prints the current memory usage
+// Don't worry about this code. You don't need to understand it.
+//
+// However, if you're curious, read on.
+//
+// The following code runs the garbage collector to clean
+// up the allocated resources, and then it reads the current
+// memory statistics into the m variable.
 func Report() {
 	var m runtime.MemStats
 	runtime.GC()

16-slices/exercises/24-fix-the-memory-leak/solution/main.go

@@ -21,25 +21,36 @@ func main() {
 	// reads 65 MB of temperature data into the memory!
 	temps := api.Read()
 
-	//
+	// ------------------------------------------------------
 	// SOLUTION #1:
-	//
+	// ------------------------------------------------------
 
-	// clone the last 10 elements of the returned temperatures
-	// into a new slice
+	//
+	// Copy the last 10 elements of the returned temperatures
+	// to a new slice.
+	//
+	// This will create a new backing array.
+	//
 	need := make([]int, 10)
 	copy(need, temps[len(temps)-10:])
-	// make the temp slice lose reference to its backing array
-	// so that it can be cleaned from the memory
+
+	//
+	// Make the temp slice lose reference to its backing array
+	// so that its backing array can be cleaned from the memory.
+	//
 	temps = need
 
-	//
+	// ------------------------------------------------------
 	// SOLUTION #2:
-	//
+	// ------------------------------------------------------
+
+	// Similar to the 1st solution. It does the same thing.
+	// But this code is more concise. Use this one.
 
-	// The code below does the same thing like the code above but in one line.
 	// temps = append([]int(nil), temps[len(temps)-10:]...)
 
+	// ------------------------------------------------------
+	// don't worry about this code yet.
 	api.Report()
 	fmt.Fprintln(ioutil.Discard, temps[0])
 }