restructure: arrays and slices

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

@@ -0,0 +1,86 @@
+// 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() {
+	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 placeholder positions (indexes).
+			// shift%l prevents the indexing error.
+			s, e := shift%l, l
+
+			// to slide the 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.
+			//
+			// shift is always increasing, for it's to go beyond the clock's length,
+			// it should be equal or greater than l*2, right (after the remainder of course)?
+			//
+			// so, if the clock goes beyond its length; this code detects that,
+			// and resets the starting position to the first placeholder's index,
+			// and it keeps doing so until the clock is fully displayed again.
+			if shift%(l*2) >= l {
+				s, e = 0, s
+			}
+
+			// print empty lines for the missing place holders.
+			// this creates the effect of moving placeholders from right to left.
+			//
+			// l-e can only be non-zero when the above if statement runs.
+			// otherwise, l-e is always zero, because l == e.
+			//
+			// this is one of the other benefits of assuming the length of the
+			// clock as the double of its length. otherwise, l-e would always be 0.
+			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-project-retro-led-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,
+}