add: array exercises

14-arrays/TODO.md

@@ -1,2 +0,0 @@
-- [ ] add challenge link to the moodly's resources
-- [ ] add exercises 1 and 2 after the array basics quiz

14-arrays/exercises/00-name/main.go

@@ -1,15 +0,0 @@
-package main
-
-// ---------------------------------------------------------
-// EXERCISE: Name
-//  ?
-//
-// NOTE
-//  ?
-//
-// EXPECTED OUTPUT
-//  ?
-// ---------------------------------------------------------
-
-func main() {
-}

14-arrays/exercises/00-name/solution/main.go

@@ -1,4 +0,0 @@
-package main
-
-func main() {
-}

14-arrays/exercises/05-fix/main.go

@@ -0,0 +1,27 @@
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Fix
+//
+//  1. Uncomment the code
+//  2. And fix the problems
+//  3. BONUS: Simplify the code
+// ---------------------------------------------------------
+
+func main() {
+	// var names [3]string = [3]string{
+	// 	"Einstein" "Shepard"
+	// 	"Tesla"
+	// }
+
+	// var books [5]string = [5]string{
+	// 	"Kafka's Revenge",
+	// 	"Stay Golden",
+	// 	"",
+	// 	"",
+	// 	""
+	// }
+
+	// fmt.Printf("%q\n", names)
+	// fmt.Printf("%q\n", books)
+}

14-arrays/exercises/05-fix/solution/main.go

@@ -0,0 +1,11 @@
+package main
+
+import "fmt"
+
+func main() {
+	names := [...]string{"Einstein", "Shepard", "Tesla"}
+	books := [5]string{"Kafka's Revenge", "Stay Golden"}
+
+	fmt.Printf("%q\n", names)
+	fmt.Printf("%q\n", books)
+}

14-arrays/exercises/06-compare/main.go

@@ -0,0 +1,34 @@
+package main
+
+import "fmt"
+
+// ---------------------------------------------------------
+// EXERCISE: Compare the Arrays
+//
+//  1. Uncomment the code
+//  2. Fix the problems so that arrays become comparable
+//
+// EXPECTED OUTPUT
+//  true
+//  true
+//  false
+// ---------------------------------------------------------
+
+func main() {
+	// week := [...]string{"Monday", "Tuesday"}
+	// wend := [4]string{"Saturday", "Sunday"}
+
+	// fmt.Println(week != wend)
+
+	// evens := [...]int{2, 4, 6, 8, 10}
+	// evens2 := [...]int32{2, 4, 6, 8, 10}
+
+	// fmt.Println(evens == evens2)
+
+	// Use     : uint8 for one of the arrays instead of byte here.
+	// Remember: Aliased types are the same types.
+	image := [5]byte{'h', 'i'}
+	var data [5]byte
+
+	fmt.Println(data == image)
+}

14-arrays/exercises/06-compare/solution/main.go

@@ -0,0 +1,22 @@
+package main
+
+import "fmt"
+
+func main() {
+	week := [...]string{"Monday", "Tuesday"}
+	wend := [...]string{"Saturday", "Sunday"}
+
+	fmt.Println(week != wend)
+
+	evens := [...]int{2, 4, 6, 8, 10}
+	evens2 := [...]int{2, 4, 6, 8, 10}
+
+	fmt.Println(evens == evens2)
+
+	// Use     : uint8 for one of the arrays instead of byte here.
+	// Remember: Aliased types are the same types.
+	image := [5]uint8{'h', 'i'}
+	var data [5]byte
+
+	fmt.Println(data == image)
+}

14-arrays/exercises/07-assign/main.go

@@ -0,0 +1,31 @@
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Assign the Arrays
+//
+//  1. Create an array named books
+//  2. Add book titles to the array
+//  3. Create two more copies of the array named: upper and lower
+//  4. Change the book titles to uppercase in the upper array only
+//  5. Change the book titles to lowercase in the lower array only
+//  6. Print all the arrays
+//  7. Observe that the arrays are not connected when they're copied.
+//
+// NOTE
+//  Check out the strings package, it has functions to convert letters to
+//  upper and lower cases.
+//
+// BONUS
+//  Invent your own arrays with different types other than string,
+//  and do some manipulations on them.
+//
+// EXPECTED OUTPUT
+//   Note: Don't worry about the book titles here, you can use any title.
+//
+//   books: ["Kafka's Revenge" "Stay Golden" "Everythingship"]
+//   upper: ["KAFKA'S REVENGE" "STAY GOLDEN" "EVERYTHINGSHIP"]
+//   lower: ["kafka's revenge" "stay golden" "everythingship"]
+// ---------------------------------------------------------
+
+func main() {
+}

14-arrays/exercises/07-assign/solution/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+func main() {
+	books := [...]string{"Kafka's Revenge", "Stay Golden", "Everythingship"}
+
+	upper, lower := books, books
+
+	for i := range books {
+		upper[i] = strings.ToUpper(upper[i])
+		lower[i] = strings.ToLower(lower[i])
+	}
+
+	fmt.Printf("books: %q\n", books)
+	fmt.Printf("upper: %q\n", upper)
+	fmt.Printf("lower: %q\n", lower)
+}

14-arrays/exercises/08-wizard-printer/main.go

@@ -0,0 +1,25 @@
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Wizard Printer
+//
+//   In this exercise, your goal is to display a few famous scientists
+//   in a pretty table.
+//
+//   1. Create a multi-dimensional array
+//   2. In each inner array, store the scientist's name, lastname and his/her
+//      nickname
+//   3. Print their information in a pretty table using a loop.
+//
+// EXPECTED OUTPUT
+//   First Name      Last Name       Nickname
+//   ==================================================
+//   Albert          Einstein        time
+//   Isaac           Newton          apple
+//   Stephen         Hawking         blackhole
+//   Marie           Curie           radium
+//   Charles         Darwin          fittest
+// ---------------------------------------------------------
+
+func main() {
+}

14-arrays/exercises/08-wizard-printer/solution/main.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+func main() {
+	names := [...][3]string{
+		{"First Name", "Last Name", "Nickname"},
+		{"Albert", "Einstein", "emc2"},
+		{"Isaac", "Newton", "apple"},
+		{"Stephen", "Hawking", "blackhole"},
+		{"Marie", "Curie", "radium"},
+		{"Charles", "Darwin", "fittest"},
+	}
+
+	for i := range names {
+		n := names[i]
+		fmt.Printf("%-15s %-15s %-15s\n", n[0], n[1], n[2])
+
+		if i == 0 {
+			fmt.Println(strings.Repeat("=", 50))
+		}
+	}
+}

14-arrays/exercises/09-currency-converter/main.go

@@ -0,0 +1,41 @@
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Currency Converter
+//
+//   In this exercise, you're going to display currency exchange ratios
+//   against USD.
+//
+//   1. Declare a few constants with iota. They're going to be the keys
+//      of the array.
+//
+//   2. Create an array that contains the conversion ratios.
+//
+//      You should use keyed elements and the contants you've declared before.
+//
+//   3. Get the USD amount to be converted from the command line.
+//
+//   4. Handle the error cases for missing or invalid input.
+//
+//   5. Print the exchange ratios.
+//
+// EXPECTED OUTPUT
+//   go run main.go
+//     Please provide the amount to be converted.
+//
+//   go run main.go invalid
+//     Invalid amount. It should be a number.
+//
+//   go run main.go 10.5
+//     10.50 USD is 9.24 EUR
+//     10.50 USD is 8.19 GBP
+//     10.50 USD is 1186.71 JPY
+//
+//   go run main.go 1
+//     1.00 USD is 0.88 EUR
+//     1.00 USD is 0.78 GBP
+//     1.00 USD is 113.02 JPY
+// ---------------------------------------------------------
+
+func main() {
+}

14-arrays/exercises/09-currency-converter/solution/main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	const (
+		EUR = iota
+		GBP
+		JPY
+	)
+
+	rates := [...]float64{
+		EUR: 0.88,
+		GBP: 0.78,
+		JPY: 113.02,
+	}
+
+	args := os.Args[1:]
+	if len(args) != 1 {
+		fmt.Println("Please provide the amount to be converted.")
+		return
+	}
+
+	amount, err := strconv.ParseFloat(args[0], 64)
+	if err != nil {
+		fmt.Println("Invalid amount. It should be a number.")
+		return
+	}
+
+	fmt.Printf("%.2f USD is %.2f EUR\n", amount, rates[EUR]*amount)
+	fmt.Printf("%.2f USD is %.2f GBP\n", amount, rates[GBP]*amount)
+	fmt.Printf("%.2f USD is %.2f JPY\n", amount, rates[JPY]*amount)
+}

14-arrays/exercises/0x-hipsters-love-search/main.go

@@ -1,24 +0,0 @@
-// 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
-
-// search for books in hipster's love
-
-// ---------------------------------------------------------
-// EXERCISE: Name
-//  ?
-//
-// NOTE
-//  ?
-//
-// EXPECTED OUTPUT
-//  ?
-// ---------------------------------------------------------
-
-func main() {
-}

14-arrays/exercises/10-hipsters-love-search/main.go

@@ -0,0 +1,56 @@
+// 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
+
+// ---------------------------------------------------------
+// EXERCISE: Hipster's Love Search Engine
+//
+//  Your goal is to let people search for books of Hipster's Love Bookstore.
+//
+//  1. Create an array with these book titles:
+//      Kafka's Revenge
+//      Stay Golden
+//      Everythingship
+//      Kafka's Revenge 2nd Edition
+//
+//  2. Get the search query from the command-line argument
+//
+//  3. Search for the books in the books array
+//
+//  4. When the programs find the book, print it.
+//  5. Otherwise, print that the book doesn't exist.
+//
+//  6. Handle the errors.
+//
+// RESTRICTION:
+//   + The search should be case insensitive.
+//
+// EXPECTED OUTPUT
+//   go run main.go
+//     Tell me a book title
+//
+//   go run main.go STAY
+//     Search Results:
+//     + Stay Golden
+//
+//   go run main.go sTaY
+//     Search Results:
+//     + Stay Golden
+//
+//   go run main.go "Kafka's Revenge"
+//     Search Results:
+//     + Kafka's Revenge
+//     + Kafka's Revenge 2nd Edition
+//
+//   go run main.go void
+//     Search Results:
+//     We don't have the book: "void"
+// ---------------------------------------------------------
+
+func main() {
+}

14-arrays/exercises/10-hipsters-love-search/solution/main.go

@@ -13,27 +13,24 @@ import (
 	"strings"
 )
 
-const yearly = 4
-
 func main() {
-	var books [yearly]string
+	books := [4]string{
+		"Kafka's Revenge",
+		"Stay Golden",
+		"Everythingship",
+		"Kafka's Revenge 2nd Edition",
+	}
 
-	books[0] = "Kafka's Revenge"
+	args := os.Args[1:]
-	books[1] = "Stay Golden"
+	if len(args) != 1 {
-	books[2] = "Everythingship"
-	books[3] += books[0] + " 2nd Edition"
-
-	if len(os.Args) != 2 {
 		fmt.Println("Tell me a book title")
 		return
 	}
-	query := os.Args[1]
+	query := strings.ToLower(args[0])
 
 	fmt.Println("Search Results:")
-	fmt.Println("---------------")
 
 	var found bool
-
 	for _, v := range books {
 		if strings.Contains(strings.ToLower(v), query) {
 			fmt.Println("+", v)
@@ -42,6 +39,6 @@ func main() {
 	}
 
 	if !found {
-		fmt.Printf("We don't have that book: %q\n", query)
+		fmt.Printf("We don't have the book: %q\n", query)
 	}
 }

14-arrays/exercises/11-average/main.go

@@ -0,0 +1,42 @@
+// 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
+
+// ---------------------------------------------------------
+// EXERCISE: Find the Average
+//
+//  Your goal is to fill an array with numbers and find the average.
+//
+//  1. Get the numbers from the command-line.
+//
+//  2. Create an array and assign the given numbers to that array.
+//
+//  3. Print the given numbers and their average.
+//
+// RESTRICTION
+//   + Maximum 5 numbers can be provided
+//   + If one of the arguments are not a valid number, skip it
+//
+// EXPECTED OUTPUT
+//   go run main.go
+//     Please tell me numbers (maximum 5 numbers).
+//
+//   go run main.go 1 2 3 4 5 6
+//     Please tell me numbers (maximum 5 numbers).
+//
+//   go run main.go 1 2 3 4 5
+//     Your numbers: [1 2 3 4 5]
+//     Average: 3
+//
+//   go run main.go 1 a 2 b 3
+//     Your numbers: [1 0 2 0 3]
+//     Average: 2
+// ---------------------------------------------------------
+
+func main() {
+}

14-arrays/exercises/11-average/solution/main.go

@@ -0,0 +1,42 @@
+// 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"
+	"os"
+	"strconv"
+)
+
+func main() {
+	args := os.Args[1:]
+	if l := len(args); l == 0 || l > 5 {
+		fmt.Println("Please tell me numbers (maximum 5 numbers).")
+		return
+	}
+
+	var (
+		sum   float64
+		nums  [5]float64
+		total float64
+	)
+
+	for i, v := range args {
+		n, err := strconv.ParseFloat(v, 64)
+		if err != nil {
+			continue
+		}
+
+		total++
+		nums[i] = n
+		sum += n
+	}
+
+	fmt.Println("Your numbers:", nums)
+	fmt.Println("Average:", sum/total)
+}

14-arrays/exercises/12-sorter/main.go

@@ -0,0 +1,41 @@
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Number Sorter
+//
+//  Your goal is to sort the given numbers from the command-line.
+//
+//  1. Get the numbers from the command-line.
+//
+//  2. Create an array and assign the given numbers to that array.
+//
+//  3. Sort the given numbers and print them.
+//
+// RESTRICTION
+//   + Maximum 5 numbers can be provided
+//   + If one of the arguments are not a valid number, skip it
+//
+// HINTS
+//  + You can use the bubble-sort algorithm to sort the numbers.
+//    Please watch this: https://youtu.be/nmhjrI-aW5o?t=7
+//
+//  + When swapping for elements, do not check for the last element.
+//    Or, you will receive this error:
+//    "panic: runtime error: index out of range"
+//
+// EXPECTED OUTPUT
+//   go run main.go
+//     Please give me up to 5 numbers.
+//
+//   go run main.go 6 5 4 3 2 1
+//     Sorry. Go arrays are fixed. So, for now, I'm only supporting sorting 5 numbers...
+//
+//   go run main.go 5 4 3 2 1
+//     [1 2 3 4 5]
+//
+//   go run main.go 5 4 a c 1
+//     [0 0 1 4 5]
+// ---------------------------------------------------------
+
+func main() {
+}

14-arrays/exercises/12-sorter/solution/main.go

@@ -0,0 +1,58 @@
+// 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"
+	"os"
+	"strconv"
+)
+
+func main() {
+	args := os.Args[1:]
+
+	switch l := len(args); {
+	case l == 0:
+		fmt.Println("Please give me up to 5 numbers.")
+		return
+	case l > 5:
+		fmt.Println("Sorry. Go arrays are fixed.",
+			"So, for now, I'm only supporting sorting 5 numbers...")
+		return
+	}
+
+	var nums [5]float64
+
+	// fill the array with the numbers
+	for i, v := range args {
+		n, err := strconv.ParseFloat(v, 64)
+		if err != nil {
+			// skip if it's not a valid number
+			continue
+		}
+
+		nums[i] = n
+	}
+
+	/*
+		check whether it's the last element or not:
+		  i < len(nums)-1
+
+		check whether the next number is greater than the current one, if so, swap it:
+		  v > nums[i+1]
+	*/
+	for range nums {
+		for i, v := range nums {
+			if i < len(nums)-1 && v > nums[i+1] {
+				nums[i], nums[i+1] = nums[i+1], nums[i]
+			}
+		}
+	}
+
+	fmt.Println(nums)
+}

14-arrays/exercises/13-word-finder/main.go

@@ -0,0 +1,48 @@
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Word Finder
+//
+//   Your goal is to search for the words inside the corpus.
+//
+//   Note: This exercise is similar to the previous word finder program:
+//   https://github.com/inancgumus/learngo/tree/master/13-loops/10-word-finder-labeled-switch
+//
+//   1. Get the search query from the command-line (it can be multiple words)
+//
+//   2. Filter these words, do not search for them:
+//      and, or, was, the, since, very
+//
+//      To do this, use an array for the filtered words.
+//
+//   3. Print the words found.
+//
+// RESTRICTION
+//   + The search and the filtering should be case insensitive
+//
+// HINT
+//   + strings.Fields function converts a given string a slice.
+//     You can find its example in the worder finder program that I've mentioned
+//     above.
+//
+// EXPECTED OUTPUT
+//   go run main.go
+//     Please give me a word to search.
+//
+//   go run main.go and was
+//
+//   go run main.go AND WAS
+//
+//   go run main.go cat beginning
+//     #2 : "cat"
+//     #11: "beginning"
+//
+//   go run main.go Cat Beginning
+//     #2 : "cat"
+//     #11: "beginning"
+// ---------------------------------------------------------
+
+const corpus = "lazy cat jumps again and again and again since the beginning this was very important"
+
+func main() {
+}

14-arrays/exercises/13-word-finder/solution/main.go

@@ -0,0 +1,48 @@
+// 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"
+	"os"
+	"strings"
+)
+
+const corpus = "lazy cat jumps again and again and again since the beginning this was very important"
+
+func main() {
+	query := os.Args[1:]
+	if len(query) == 0 {
+		fmt.Println("Please give me a word to search.")
+		return
+	}
+
+	filter := [...]string{
+		"and", "or", "was", "the", "since", "very",
+	}
+
+	words := strings.Fields(strings.ToLower(corpus))
+
+queries:
+	for _, q := range query {
+		q = strings.ToLower(q)
+
+		for _, v := range filter {
+			if q == v {
+				continue queries
+			}
+		}
+
+		for i, w := range words {
+			if q == w {
+				fmt.Printf("#%-2d: %q\n", i+1, w)
+				break
+			}
+		}
+	}
+}

14-arrays/exercises/IDEAS.md

@@ -1,13 +0,0 @@
-# Array Exercises
-
-- get data from command-line
-  - into a fixed array; see how it blows beyond its len
-
-- add items
-- get items
-- check the length
-- reverse the array
-- shuffle the items
-- find the first item that contains x
-- find the last item that contains y
-- find the duplicate items

14-arrays/exercises/README.md

@@ -1,6 +1,6 @@
 # Array Exercises
 
-## Basic Exercises
+## Exercises Level I - Basics
 
 1. **[Declare Empty Arrays](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/01-declare-empty)**
 
@@ -10,10 +10,24 @@
 
 4. **[Refactor to Ellipsis](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/04-ellipsis)**
 
+5. **[Fix](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/05-fix)**
+
+6. **[Compare the Arrays](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/06-compare)**
+
+7. **[Assign the Arrays](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/07-assign)**
+
 ---
 
-## Program Exercises
+## Exercises Level II
 
-????. **[text](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/)**
+1. **[Wizard Printer](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/08-wizard-printer)**
 
-    ?
+2. **[Currency Converter](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/09-currency-converter)**
+
+3. **[Hipster's Bookstore Search Engine](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/10-hipsters-love-search)**
+
+4. **[Find the Average](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/11-average)**
+
+5. **[Number Sorter](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/12-sorter)**
+   
+6. **[Word Finder](https://github.com/inancgumus/learngo/tree/master/14-arrays/exercises/13-word-finder)**

etc/stratch/main.go

@@ -1,42 +1,4 @@
 package main
 
-import "fmt"
-
 func main() {
-	students := [...][3]float64{
-		{5, 6, 1},
-		{9, 8, 4},
-	}
-
-	var sum float64
-	for _, grades := range students {
-		for _, grade := range grades {
-			sum += grade
-		}
-	}
-
-	const N = float64(len(students) * len(students[0]))
-	fmt.Printf("Avg Grade: %g\n", sum/N)
-
-	// students := [2][3]float64{
-	// 	[3]float64{5, 6, 1},
-	// 	[3]float64{9, 8, 4},
-	// }
-
-	// var sum float64
-	// sum += students[0][0] + students[0][1] + students[0][2]
-	// sum += students[1][0] + students[1][1] + students[1][2]
-
-	// const N = float64(len(students) * len(students[0]))
-	// fmt.Printf("Avg Grade: %g\n", sum/N)
-
-	// student1 := [3]float64{5, 6, 1}
-	// student2 := [3]float64{9, 8, 4}
-
-	// var sum float64
-	// sum += student1[0] + student1[1] + student1[2]
-	// sum += student2[0] + student2[1] + student2[2]
-
-	// const N = float64(len(student1) * 2)
-	// fmt.Printf("Avg Grade: %g\n", sum/N)
 }

x-tba/17-strings-revisited/exercises/_exp/fromarrays/main.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+// ---------------------------------------------------------
+// EXERCISE: Assign the Arrays
+//
+//  1. Create an array named books
+//  2. Add book titles to the array
+//  3. Create two more copies of the array named: upper and lower
+//  4. Change the book titles to uppercase in the upper array only
+//  5. Change the book titles to lowercase in the lower array only
+//  6. Print all the arrays
+//
+// NOTE
+//  Check out the strings package, it has function to convert cases to
+//  upper and lower cases.
+//
+// BONUS
+//  1. Invent your own arrays with different types other than string,
+//     and do some manipulations on them.
+//
+//  👉 THISSSS--------------------------------------------------------
+//  2. Find some Turkish book titles and do the same upper, lowercase conversion
+//     for them.
+//
+//     Here are some books: https://www.goodreads.com/group/bookshelf/417154-bilimkurgu-kul-b?shelf=read
+//
+//     Note: You'd need to use special functions to convert the Turkish letters.
+//           They're in the strings package as well.
+//
+// EXPECTED OUTPUT
+//  ?
+// ---------------------------------------------------------
+
+func main() {
+	books := [...]string{"Kafka's Revenge", "Stay Golden", "Everythingship"}
+
+	upper, lower := books, books
+
+	for i := range books {
+		upper[i] = strings.ToUpper(upper[i])
+		lower[i] = strings.ToLower(lower[i])
+	}
+
+	fmt.Printf("books: %q\n", books)
+	fmt.Printf("upper: %q\n", upper)
+	fmt.Printf("lower: %q\n", lower)
+}