add: array led clock exercises

15-arrays-project-clock/exercises/00-text/main.go

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+// 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: Text
+//
+//  1. Text
+//
+// HINT
+//   Text
+//
+// EXPECTED OUTPUT
+//  Text
+// ---------------------------------------------------------
+
+func main() {
+}

15-arrays-project-clock/exercises/00-text/solution/main.go

@@ -0,0 +1,11 @@
+// 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
+
+func main() {
+}

15-arrays-project-clock/exercises/01-refactor/main.go

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+// 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/
+//
+
+// ---------------------------------------------------------
+// EXERCISE: Refactor
+//
+//  Goal is refactoring the clock project by moving some of its parts to
+//  a new file in the same package.
+//
+//  1. Create a new file: placeholders.go
+//  2. Move the placeholder type to placeholder.go
+//  3. Move all the placeholders (zero to nine and the colon) to placeholder.go
+//  4. Move the digits array to placeholders.go
+//
+// HINT
+//  + placeholders.go file should belong to main package as well
+//
+//    To remember how to do so: Rewatch the "PART I — Packages, Scopes and Importing"
+//    section.
+//
+//  + Short declaration won't work in the package scope.
+//    Remember why by watching: "Short Declaration: Package Scope" lecture
+//
+//  + If you receive the following error and you don't know what to do watch:
+//    "Packages - Learn how to run multiple files" lecture.
+//
+//    # command-line-arguments
+//    undefined: placeholder
+//    undefined: colon
+//
+// EXPECTED OUTPUT
+//  The same output before the refactoring.
+// ---------------------------------------------------------
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	type placeholder [5]string
+
+	zero := placeholder{
+		"███",
+		"█ █",
+		"█ █",
+		"█ █",
+		"███",
+	}
+
+	one := placeholder{
+		"██ ",
+		" █ ",
+		" █ ",
+		" █ ",
+		"███",
+	}
+
+	two := placeholder{
+		"███",
+		"  █",
+		"███",
+		"█  ",
+		"███",
+	}
+
+	three := placeholder{
+		"███",
+		"  █",
+		"███",
+		"  █",
+		"███",
+	}
+
+	four := placeholder{
+		"█ █",
+		"█ █",
+		"███",
+		"  █",
+		"  █",
+	}
+
+	five := placeholder{
+		"███",
+		"█  ",
+		"███",
+		"  █",
+		"███",
+	}
+
+	six := placeholder{
+		"███",
+		"█  ",
+		"███",
+		"█ █",
+		"███",
+	}
+
+	seven := placeholder{
+		"███",
+		"  █",
+		"  █",
+		"  █",
+		"  █",
+	}
+
+	eight := placeholder{
+		"███",
+		"█ █",
+		"███",
+		"█ █",
+		"███",
+	}
+
+	nine := placeholder{
+		"███",
+		"█ █",
+		"███",
+		"  █",
+		"███",
+	}
+
+	colon := placeholder{
+		"   ",
+		" ░ ",
+		"   ",
+		" ░ ",
+		"   ",
+	}
+
+	digits := [...]placeholder{
+		zero, one, two, three, four, five, six, seven, eight, nine,
+	}
+
+	screen.Clear()
+
+	for {
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		for line := range clock[0] {
+			for index, digit := range clock {
+				// colon blink
+				next := clock[index][line]
+				if digit == colon && sec%2 == 0 {
+					next = "   "
+				}
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		time.Sleep(time.Second)
+	}
+}

15-arrays-project-clock/exercises/01-refactor/solution/main.go

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+// 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"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	screen.Clear()
+
+	for {
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		for line := range clock[0] {
+			for index, digit := range clock {
+				// colon blink
+				next := clock[index][line]
+				if digit == colon && sec%2 == 0 {
+					next = "   "
+				}
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		time.Sleep(time.Second)
+	}
+}

15-arrays-project-clock/exercises/01-refactor/solution/placeholders.go

@@ -0,0 +1,95 @@
+package main
+
+type placeholder [5]string
+
+var zero = placeholder{
+	"███",
+	"█ █",
+	"█ █",
+	"█ █",
+	"███",
+}
+
+var one = placeholder{
+	"██ ",
+	" █ ",
+	" █ ",
+	" █ ",
+	"███",
+}
+
+var two = placeholder{
+	"███",
+	"  █",
+	"███",
+	"█  ",
+	"███",
+}
+
+var three = placeholder{
+	"███",
+	"  █",
+	"███",
+	"  █",
+	"███",
+}
+
+var four = placeholder{
+	"█ █",
+	"█ █",
+	"███",
+	"  █",
+	"  █",
+}
+
+var five = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"  █",
+	"███",
+}
+
+var six = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"█ █",
+	"███",
+}
+
+var seven = placeholder{
+	"███",
+	"  █",
+	"  █",
+	"  █",
+	"  █",
+}
+
+var eight = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"█ █",
+	"███",
+}
+
+var nine = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"  █",
+	"███",
+}
+
+var colon = placeholder{
+	"   ",
+	" ░ ",
+	"   ",
+	" ░ ",
+	"   ",
+}
+
+var digits = [...]placeholder{
+	zero, one, two, three, four, five, six, seven, eight, nine,
+}

15-arrays-project-clock/exercises/02-alarm/main.go

@@ -0,0 +1,87 @@
+// 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/
+//
+
+// ---------------------------------------------------------
+// EXERCISE: Set an Alarm
+//
+//  Goal is printing " ALARM! " every 10 seconds.
+//
+// EXPECTED OUTPUT
+//
+//     ██   ███       ███  ██        ███  ███
+//      █     █   ░     █   █    ░     █  █ █
+//      █   ███       ███   █        ███  ███
+//      █   █     ░     █   █    ░     █    █
+//     ███  ███       ███  ███       ███  ███
+//
+//          ███  █    ███  ██   █ █   █
+//          █ █  █    █ █  █ █  ███   █
+//          ███  █    ███  ██   █ █   █
+//          █ █  █    █ █  █ █  █ █
+//          █ █  ███  █ █  █ █  █ █   █
+//
+//     ██   ███       ███  ██        █ █  ██
+//      █     █   ░     █   █    ░   █ █   █
+//      █   ███       ███   █        ███   █
+//      █   █     ░     █   █    ░     █   █
+//     ███  ███       ███  ███         █  ███
+//
+// HINTS
+//
+//  <<< BEWARE THE SPOILER! >>>
+//
+//  I recommend you to first solve the exercise yourself before reading the
+//  following hint.
+//
+//
+//  + You can create a new array named alarm with the same length of the
+//    clocks array, so you can copy the alarm array to the clocks array
+//    every 10 seconds.
+//
+// ---------------------------------------------------------
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	screen.Clear()
+
+	for {
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		for line := range clock[0] {
+			for index, digit := range clock {
+				// colon blink
+				next := clock[index][line]
+				if digit == colon && sec%2 == 0 {
+					next = "   "
+				}
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		time.Sleep(time.Second)
+	}
+}

15-arrays-project-clock/exercises/02-alarm/placeholders.go

@@ -0,0 +1,95 @@
+package main
+
+type placeholder [5]string
+
+var zero = placeholder{
+	"███",
+	"█ █",
+	"█ █",
+	"█ █",
+	"███",
+}
+
+var one = placeholder{
+	"██ ",
+	" █ ",
+	" █ ",
+	" █ ",
+	"███",
+}
+
+var two = placeholder{
+	"███",
+	"  █",
+	"███",
+	"█  ",
+	"███",
+}
+
+var three = placeholder{
+	"███",
+	"  █",
+	"███",
+	"  █",
+	"███",
+}
+
+var four = placeholder{
+	"█ █",
+	"█ █",
+	"███",
+	"  █",
+	"  █",
+}
+
+var five = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"  █",
+	"███",
+}
+
+var six = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"█ █",
+	"███",
+}
+
+var seven = placeholder{
+	"███",
+	"  █",
+	"  █",
+	"  █",
+	"  █",
+}
+
+var eight = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"█ █",
+	"███",
+}
+
+var nine = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"  █",
+	"███",
+}
+
+var colon = placeholder{
+	"   ",
+	" ░ ",
+	"   ",
+	" ░ ",
+	"   ",
+}
+
+var digits = [...]placeholder{
+	zero, one, two, three, four, five, six, seven, eight, nine,
+}

15-arrays-project-clock/exercises/02-alarm/solution/main.go

@@ -0,0 +1,53 @@
+// 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"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	screen.Clear()
+
+	for {
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		alarmed := sec%10 == 0
+
+		for line := range clock[0] {
+			if alarmed {
+				clock = alarm
+			}
+
+			for index, digit := range clock {
+				next := clock[index][line]
+				if digit == colon && sec%2 == 0 {
+					next = "   "
+				}
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		time.Sleep(time.Second)
+	}
+}

15-arrays-project-clock/exercises/02-alarm/solution/placeholders.go

@@ -0,0 +1,154 @@
+package main
+
+type placeholder [5]string
+
+var zero = placeholder{
+	"███",
+	"█ █",
+	"█ █",
+	"█ █",
+	"███",
+}
+
+var one = placeholder{
+	"██ ",
+	" █ ",
+	" █ ",
+	" █ ",
+	"███",
+}
+
+var two = placeholder{
+	"███",
+	"  █",
+	"███",
+	"█  ",
+	"███",
+}
+
+var three = placeholder{
+	"███",
+	"  █",
+	"███",
+	"  █",
+	"███",
+}
+
+var four = placeholder{
+	"█ █",
+	"█ █",
+	"███",
+	"  █",
+	"  █",
+}
+
+var five = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"  █",
+	"███",
+}
+
+var six = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"█ █",
+	"███",
+}
+
+var seven = placeholder{
+	"███",
+	"  █",
+	"  █",
+	"  █",
+	"  █",
+}
+
+var eight = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"█ █",
+	"███",
+}
+
+var nine = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"  █",
+	"███",
+}
+
+var colon = placeholder{
+	"   ",
+	" ░ ",
+	"   ",
+	" ░ ",
+	"   ",
+}
+
+var alarm = [...]placeholder{
+	{
+		"   ",
+		"   ",
+		"   ",
+		"   ",
+		"   ",
+	},
+	{
+		"███",
+		"█ █",
+		"███",
+		"█ █",
+		"█ █",
+	},
+	{
+		"█  ",
+		"█  ",
+		"█  ",
+		"█  ",
+		"███",
+	},
+	{
+		"███",
+		"█ █",
+		"███",
+		"█ █",
+		"█ █",
+	},
+	{
+		"██ ",
+		"█ █",
+		"██ ",
+		"█ █",
+		"█ █",
+	},
+	{
+		"█ █",
+		"███",
+		"█ █",
+		"█ █",
+		"█ █",
+	},
+	{
+		" █ ",
+		" █ ",
+		" █ ",
+		"   ",
+		" █ ",
+	},
+	{
+		"   ",
+		"   ",
+		"   ",
+		"   ",
+		"   ",
+	},
+}
+
+var digits = [...]placeholder{
+	zero, one, two, three, four, five, six, seven, eight, nine,
+}

15-arrays-project-clock/exercises/03-split-second/main.go

@@ -0,0 +1,147 @@
+// 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/
+//
+
+// ---------------------------------------------------------
+// EXERCISE: Add Split Seconds
+//
+//  Your goal is adding the split second to the clock. A split second is
+//  1/10th of a second.
+//
+//  1. Find the current split second
+//  2. Add dot character to the clock (as in the expected output)
+//  3. Add the split second digit to the clock
+//  4. Blink the dot every two seconds (just like the separators)
+//  5. Update the clock every 1/10th of a second, instead of every second.
+//     (Update the clock every 100 millliseconds)
+//
+// HINTS
+//   + You can find the split second using Nanosecond method of the Time type.
+//     https://golang.org/pkg/time/#Time.Nanosecond
+//
+//   + A split second is the first digit of the Nanosecond.
+//
+//   + Remember: time.Second is an integer constant, so it can be divided
+//               with a number.
+//
+//     https://golang.org/pkg/time/#Time.Second
+//
+// EXPECTED OUTPUT
+//     Note that, clock is updated every split second instead of a second.
+//
+//     Separators are displayed (second is an odd number):
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █    ░   █     █    ░    █     █       █ █
+//      █    █        ███   █         █     █       █ █
+//      █    █    ░     █   █    ░    █     █       █ █
+//     ███  ███       ███  ███       ███    █   ░   ███
+//
+//     ██   ██        ███  ██        ██   ███       ██
+//      █    █    ░   █     █    ░    █     █        █
+//      █    █        ███   █         █     █        █
+//      █    █    ░     █   █    ░    █     █        █
+//     ███  ███       ███  ███       ███    █   ░   ███
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █    ░   █     █    ░    █     █         █
+//      █    █        ███   █         █     █       ███
+//      █    █    ░     █   █    ░    █     █       █
+//     ███  ███       ███  ███       ███    █   ░   ███
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █    ░   █     █    ░    █     █         █
+//      █    █        ███   █         █     █       ███
+//      █    █    ░     █   █    ░    █     █         █
+//     ███  ███       ███  ███       ███    █   ░   ███
+//
+//     ██   ██        ███  ██        ██   ███       █ █
+//      █    █    ░   █     █    ░    █     █       █ █
+//      █    █        ███   █         █     █       ███
+//      █    █    ░     █   █    ░    █     █         █
+//     ███  ███       ███  ███       ███    █   ░     █
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █    ░   █     █    ░    █     █       █
+//      █    █        ███   █         █     █       ███
+//      █    █    ░     █   █    ░    █     █         █
+//     ███  ███       ███  ███       ███    █   ░   ███
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █    ░   █     █    ░    █     █       █
+//      █    █        ███   █         █     █       ███
+//      █    █    ░     █   █    ░    █     █       █ █
+//     ███  ███       ███  ███       ███    █   ░   ███
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █    ░   █     █    ░    █     █         █
+//      █    █        ███   █         █     █         █
+//      █    █    ░     █   █    ░    █     █         █
+//     ███  ███       ███  ███       ███    █   ░     █
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █    ░   █     █    ░    █     █       █ █
+//      █    █        ███   █         █     █       ███
+//      █    █    ░     █   █    ░    █     █       █ █
+//     ███  ███       ███  ███       ███    █   ░   ███
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █    ░   █     █    ░    █     █       █ █
+//      █    █        ███   █         █     █       ███
+//      █    █    ░     █   █    ░    █     █         █
+//     ███  ███       ███  ███       ███    █   ░   ███
+//
+//     Separators are not displayed (second is an even number):
+//
+//     ██   ██        ███  ██        ██   ███       ███
+//      █    █        █     █         █   █ █       █ █
+//      █    █        ███   █         █   ███       █ █
+//      █    █          █   █         █   █ █       █ █
+//     ███  ███       ███  ███       ███  ███       ███
+//
+// ---------------------------------------------------------
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	screen.Clear()
+
+	for {
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		for line := range clock[0] {
+			for index, digit := range clock {
+				// colon blink
+				next := clock[index][line]
+				if digit == colon && sec%2 == 0 {
+					next = "   "
+				}
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		time.Sleep(time.Second)
+	}
+}

15-arrays-project-clock/exercises/03-split-second/placeholders.go

@@ -0,0 +1,95 @@
+package main
+
+type placeholder [5]string
+
+var zero = placeholder{
+	"███",
+	"█ █",
+	"█ █",
+	"█ █",
+	"███",
+}
+
+var one = placeholder{
+	"██ ",
+	" █ ",
+	" █ ",
+	" █ ",
+	"███",
+}
+
+var two = placeholder{
+	"███",
+	"  █",
+	"███",
+	"█  ",
+	"███",
+}
+
+var three = placeholder{
+	"███",
+	"  █",
+	"███",
+	"  █",
+	"███",
+}
+
+var four = placeholder{
+	"█ █",
+	"█ █",
+	"███",
+	"  █",
+	"  █",
+}
+
+var five = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"  █",
+	"███",
+}
+
+var six = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"█ █",
+	"███",
+}
+
+var seven = placeholder{
+	"███",
+	"  █",
+	"  █",
+	"  █",
+	"  █",
+}
+
+var eight = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"█ █",
+	"███",
+}
+
+var nine = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"  █",
+	"███",
+}
+
+var colon = placeholder{
+	"   ",
+	" ░ ",
+	"   ",
+	" ░ ",
+	"   ",
+}
+
+var digits = [...]placeholder{
+	zero, one, two, three, four, five, six, seven, eight, nine,
+}

15-arrays-project-clock/exercises/03-split-second/solution/main.go

@@ -0,0 +1,51 @@
+// 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"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	screen.Clear()
+
+	for {
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+		ssec := now.Nanosecond() / 1e8
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+			dot,
+			digits[ssec],
+		}
+
+		for line := range clock[0] {
+			for index, digit := range clock {
+				next := clock[index][line]
+				if (digit == colon || digit == dot) && sec%2 == 0 {
+					next = "   "
+				}
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		const splitSecond = time.Second / 10
+		time.Sleep(splitSecond)
+	}
+}

15-arrays-project-clock/exercises/03-split-second/solution/placeholders.go

@@ -0,0 +1,103 @@
+package main
+
+type placeholder [5]string
+
+var zero = placeholder{
+	"███",
+	"█ █",
+	"█ █",
+	"█ █",
+	"███",
+}
+
+var one = placeholder{
+	"██ ",
+	" █ ",
+	" █ ",
+	" █ ",
+	"███",
+}
+
+var two = placeholder{
+	"███",
+	"  █",
+	"███",
+	"█  ",
+	"███",
+}
+
+var three = placeholder{
+	"███",
+	"  █",
+	"███",
+	"  █",
+	"███",
+}
+
+var four = placeholder{
+	"█ █",
+	"█ █",
+	"███",
+	"  █",
+	"  █",
+}
+
+var five = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"  █",
+	"███",
+}
+
+var six = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"█ █",
+	"███",
+}
+
+var seven = placeholder{
+	"███",
+	"  █",
+	"  █",
+	"  █",
+	"  █",
+}
+
+var eight = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"█ █",
+	"███",
+}
+
+var nine = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"  █",
+	"███",
+}
+
+var colon = placeholder{
+	"   ",
+	" ░ ",
+	"   ",
+	" ░ ",
+	"   ",
+}
+
+var dot = placeholder{
+	"   ",
+	"   ",
+	"   ",
+	"   ",
+	" ░ ",
+}
+
+var digits = [...]placeholder{
+	zero, one, two, three, four, five, six, seven, eight, nine,
+}

15-arrays-project-clock/exercises/04-ticker/main.go

@@ -0,0 +1,113 @@
+// 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/
+//
+
+// ---------------------------------------------------------
+// EXERCISE: Ticker: Slide the Clock
+//
+//  Your goal is slide the placeholders every second.
+//  Please run the solution to see it in action.
+//
+//
+//  THIS IS A HARD EXERCISE:
+//  + It will take you days but it will worth it.
+//  + For experienced developers, this can take an hour or so.
+//
+//
+//  1. You need to determine the starting and the ending digits to create
+//     the sliding effect.
+//
+//
+//  2. Each second, start from the next placeholder, skip the previous one.
+//     This means: Only draw the next placeholders.
+//
+//     Like this:
+//
+//     12:40:31
+//     2:40:31
+//     40:31
+//     0:31
+//     :31
+//     31
+//     1
+//
+//
+//  3. After the last placeholder is displayed, fill the lines for the missing
+//     placeholders, and then start from the first placeholder. Draw it to the
+//     right part of the screen.
+//
+//     Like this:
+//
+//     12:40:31
+//     2:40:31
+//     40:31
+//     0:31
+//     :31
+//     31
+//     1
+//            1
+//           31
+//          :31
+//         0:31
+//        40:31
+//       :40:31
+//      2:40:31
+//     12:40:31
+//
+//     As you can see, you need to draw the clock from the right part of the
+//     screen, beginning from the first placeholder.
+//
+//
+// HINTS
+//   + You would need to clear the screen inside the loop instead of once.
+//     Otherwise the previous placeholders will be left on the screen.
+//
+//
+// EXPECTED OUTPUT
+//   Please run the solution to see it in action. Do not look at the source-code
+//   though.
+// ---------------------------------------------------------
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	screen.Clear()
+
+	for {
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		for line := range clock[0] {
+			for index, digit := range clock {
+				next := clock[index][line]
+				if digit == colon && sec%2 == 0 {
+					next = "   "
+				}
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		time.Sleep(time.Second)
+	}
+}

15-arrays-project-clock/exercises/04-ticker/placeholders.go

@@ -0,0 +1,95 @@
+package main
+
+type placeholder [5]string
+
+var zero = placeholder{
+	"███",
+	"█ █",
+	"█ █",
+	"█ █",
+	"███",
+}
+
+var one = placeholder{
+	"██ ",
+	" █ ",
+	" █ ",
+	" █ ",
+	"███",
+}
+
+var two = placeholder{
+	"███",
+	"  █",
+	"███",
+	"█  ",
+	"███",
+}
+
+var three = placeholder{
+	"███",
+	"  █",
+	"███",
+	"  █",
+	"███",
+}
+
+var four = placeholder{
+	"█ █",
+	"█ █",
+	"███",
+	"  █",
+	"  █",
+}
+
+var five = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"  █",
+	"███",
+}
+
+var six = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"█ █",
+	"███",
+}
+
+var seven = placeholder{
+	"███",
+	"  █",
+	"  █",
+	"  █",
+	"  █",
+}
+
+var eight = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"█ █",
+	"███",
+}
+
+var nine = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"  █",
+	"███",
+}
+
+var colon = placeholder{
+	"   ",
+	" ░ ",
+	"   ",
+	" ░ ",
+	"   ",
+}
+
+var digits = [...]placeholder{
+	zero, one, two, three, four, five, six, seven, eight, nine,
+}

15-arrays-project-clock/exercises/04-ticker/solution/main.go

@@ -0,0 +1,78 @@
+// 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"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	// by using 'shift' we can create the slide effect for placeholders.
+	for shift := 0; ; shift++ {
+		// we need to clear the screen here.
+		// or the previous character will be left on the screen
+		//
+		// alternative: you can fill the rest of the missing placeholders
+		//              with empty lines
+		screen.Clear()
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		for line := range clock[0] {
+			l := len(clock)
+
+			// this sets the beginning and the ending placeholders.
+			// to prevent the indexing error: we use the remainder operator.
+			s, e := shift%l, l
+
+			// to slide placeholders from the right part of the screen.
+			//
+			// here, we assume that as if the clock's length is double of its length.
+			// this makes things easy to manage: that's why: l*2 is there.
+			//
+			// whenever, the current shift factor's double remainder is greater than
+			// the length of the clock - 1, it changes the starting and ending positions.
+			if shift%(l*2) > l-1 {
+				s, e = 0, shift%l+1
+			}
+
+			// print empty lines for the right-to-left slide effect.
+			//
+			// this creates the effect of moving placeholders from right to left.
+			for j := 0; j < l-e; j++ {
+				fmt.Print("     ")
+			}
+
+			// draw the digits starting from 's' to 'e'
+			for i := s; i < e; i++ {
+				next := clock[i][line]
+				if clock[i] == colon && sec%2 == 0 {
+					next = "   "
+				}
+
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		time.Sleep(time.Second)
+	}
+}

15-arrays-project-clock/exercises/04-ticker/solution/placeholders.go

@@ -0,0 +1,95 @@
+package main
+
+type placeholder [5]string
+
+var zero = placeholder{
+	"███",
+	"█ █",
+	"█ █",
+	"█ █",
+	"███",
+}
+
+var one = placeholder{
+	"██ ",
+	" █ ",
+	" █ ",
+	" █ ",
+	"███",
+}
+
+var two = placeholder{
+	"███",
+	"  █",
+	"███",
+	"█  ",
+	"███",
+}
+
+var three = placeholder{
+	"███",
+	"  █",
+	"███",
+	"  █",
+	"███",
+}
+
+var four = placeholder{
+	"█ █",
+	"█ █",
+	"███",
+	"  █",
+	"  █",
+}
+
+var five = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"  █",
+	"███",
+}
+
+var six = placeholder{
+	"███",
+	"█  ",
+	"███",
+	"█ █",
+	"███",
+}
+
+var seven = placeholder{
+	"███",
+	"  █",
+	"  █",
+	"  █",
+	"  █",
+}
+
+var eight = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"█ █",
+	"███",
+}
+
+var nine = placeholder{
+	"███",
+	"█ █",
+	"███",
+	"  █",
+	"███",
+}
+
+var colon = placeholder{
+	"   ",
+	" ░ ",
+	"   ",
+	" ░ ",
+	"   ",
+}
+
+var digits = [...]placeholder{
+	zero, one, two, three, four, five, six, seven, eight, nine,
+}

15-arrays-project-clock/exercises/README.md

@@ -0,0 +1,21 @@
+# Exercises
+
+These exercises will reinforce your knowledge of manipulating arrays. You will prove yourself that you can write easy to maintain Go programs.
+
+1. **[Refactor](https://github.com/inancgumus/learngo/tree/master/15-arrays-project-clock/exercises/01-refactor)**
+
+  In this exercise, you will refactor the project to multiple files by moving
+  all the placeholders. This will make the project easy to maintain down the road.
+
+2. **[Set an Alarm](https://github.com/inancgumus/learngo/tree/master/15-arrays-project-clock/exercises/02-alarm)**
+
+  You will print " ALARM! " every 10 seconds.
+
+3. **[Split Second](https://github.com/inancgumus/learngo/tree/master/15-arrays-project-clock/exercises/03-split-second)**
+
+  You will display the split second in the clock, you will need to update the
+  clock every 1/10th of a second instead of every second.
+
+4. **[Ticker](https://github.com/inancgumus/learngo/tree/master/15-arrays-project-clock/exercises/04-ticker)**
+
+  This is an HARD EXERCISE. You will slide the clock animation from right-to-left. After this exercise, you will truly feel that you've mastered everything you've learned so far.

etc/stratch/main.go

@@ -1,129 +1,4 @@
 package main
 
-import (
-	"fmt"
-	"time"
-
-	"github.com/inancgumus/screen"
-)
-
 func main() {
-	type placeholder [5]string
-
-	zero := placeholder{"███", "█ █", "█ █", "█ █", "███"}
-	one := placeholder{"██ ",
-		" █ ",
-		" █ ",
-		" █ ",
-		"███",
-	}
-
-	two := placeholder{
-		"███",
-		"  █",
-		"███",
-		"█  ",
-		"███",
-	}
-
-	three := placeholder{
-		"███",
-		"  █",
-		"███",
-		"  █",
-		"███",
-	}
-
-	four := placeholder{
-		"█ █",
-		"█ █",
-		"███",
-		"  █",
-		"  █",
-	}
-
-	five := placeholder{
-		"███",
-		"█  ",
-		"███",
-		"  █",
-		"███",
-	}
-
-	six := placeholder{
-		"███",
-		"█  ",
-		"███",
-		"█ █",
-		"███",
-	}
-
-	seven := placeholder{
-		"███",
-		"  █",
-		"  █",
-		"  █",
-		"  █",
-	}
-
-	eight := placeholder{
-		"███",
-		"█ █",
-		"███",
-		"█ █",
-		"███",
-	}
-
-	nine := placeholder{
-		"███",
-		"█ █",
-		"███",
-		"  █",
-		"███",
-	}
-
-	colon := placeholder{
-		"   ",
-		" ░ ",
-		"   ",
-		" ░ ",
-		"   ",
-	}
-
-	digits := [...]placeholder{
-		zero, one, two, three, four, five, six, seven, eight, nine,
-	}
-
-	screen.Clear()
-
-	for {
-		screen.MoveTopLeft()
-
-		now := time.Now()
-		hour, min, sec := now.Hour(), now.Minute(), now.Second()
-
-		// [8][5]string -> [8]placeholder
-		clock := [...]placeholder{
-			digits[hour/10], digits[hour%10],
-			colon,
-			digits[min/10], digits[min%10],
-			colon,
-			digits[sec/10], digits[sec%10],
-		}
-
-		for line := range clock[0] {
-			for index, digit := range clock {
-				next := clock[index][line]
-				if digit == colon && sec%2 == 0 {
-					next = "   "
-				}
-
-				fmt.Print(next, "  ")
-			}
-			fmt.Println()
-		}
-		fmt.Println()
-
-		time.Sleep(time.Second)
-	}
 }