restructure: arrays and slices

15-project-retro-led-clock/05-full-annotated-solution/main.go

@@ -0,0 +1,178 @@
+// 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 keeping things easy to read and type-safe
+	type placeholder [5]string
+
+	// put the digits (placeholders) into variables
+	// using the placeholder array type above
+	zero := placeholder{
+		"███",
+		"█ █",
+		"█ █",
+		"█ █",
+		"███",
+	}
+
+	one := placeholder{
+		"██ ",
+		" █ ",
+		" █ ",
+		" █ ",
+		"███",
+	}
+
+	two := placeholder{
+		"███",
+		"  █",
+		"███",
+		"█  ",
+		"███",
+	}
+
+	three := placeholder{
+		"███",
+		"  █",
+		"███",
+		"  █",
+		"███",
+	}
+
+	four := placeholder{
+		"█ █",
+		"█ █",
+		"███",
+		"  █",
+		"  █",
+	}
+
+	five := placeholder{
+		"███",
+		"█  ",
+		"███",
+		"  █",
+		"███",
+	}
+
+	six := placeholder{
+		"███",
+		"█  ",
+		"███",
+		"█ █",
+		"███",
+	}
+
+	seven := placeholder{
+		"███",
+		"  █",
+		"  █",
+		"  █",
+		"  █",
+	}
+
+	eight := placeholder{
+		"███",
+		"█ █",
+		"███",
+		"█ █",
+		"███",
+	}
+
+	nine := placeholder{
+		"███",
+		"█ █",
+		"███",
+		"  █",
+		"███",
+	}
+
+	colon := placeholder{
+		"   ",
+		" ░ ",
+		"   ",
+		" ░ ",
+		"   ",
+	}
+
+	// This array's type is "like": [10][5]string
+	//
+	// However:
+	// + "placeholder" is not equal to [5]string in type-wise.
+	// + Because: "placeholder" is a defined type, which is different
+	//   from [5]string type.
+	// + [5]string is an unnamed type.
+	// + placeholder is a named type.
+	// + The underlying type of [5]string and placeholder is the same:
+	//     [5]string
+	digits := [...]placeholder{
+		zero, one, two, three, four, five, six, seven, eight, nine,
+	}
+
+	// For Go Playground, do not use this.
+	screen.Clear()
+
+	// Go Playground will not run an infinite loop.
+	// Loop for example 1000 times instead, like this:
+	//   for i := 0; i < 1000; i++ { ... }
+	for {
+		// For Go Playground, use this instead:
+		// fmt.Print("\f")
+		screen.MoveTopLeft()
+
+		// get the current hour, minute and second
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		// extract the digits: 17 becomes, 1 and 7 respectively
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		// Explanation: clock[0]
+		// + Each element of clock has the same length.
+		// + So: Getting the length of only one element is OK.
+		// + This could be: "zero" or "one" and so on... Instead of: digits[0]
+		//
+		// The range clause below is ~equal to the following code:
+		//   line := 0; line < len(clock[0]); line++
+		for line := range clock[0] {
+			// Print a line for each placeholder in clock
+			for index, digit := range clock {
+				// Colon blink on every two seconds.
+				// + On each sec divisible by two, prints an empty line
+				// + Otherwise: prints the current pixel
+				next := clock[index][line]
+				if digit == colon && sec%2 == 0 {
+					next = "   "
+				}
+				// Print the next line and,
+				// give it enough space for the next placeholder
+				fmt.Print(next, "  ")
+			}
+
+			// After each line of a placeholder, print a newline
+			fmt.Println()
+		}
+
+		// pause for 1 second
+		time.Sleep(time.Second)
+	}
+}