Initial commit

10-constants/03-refactor-feet-to-meters/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"
+	"os"
+	"strconv"
+)
+
+// EXERCISE
+//
+// This program uses magic numbers
+// Refactor it and use named constants instead
+
+func main() {
+	arg := os.Args[1]
+
+	feet, _ := strconv.ParseFloat(arg, 64)
+
+	meters := feet * 0.3048
+	yards := feet * 0.3333
+
+	fmt.Printf("%g feet is %g meters.\n", feet, meters)
+	fmt.Printf("%g feet is %g yards.\n", feet, yards)
+}

10-constants/03-refactor-feet-to-meters/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"
+	"math"
+	"os"
+	"strconv"
+)
+
+// This program contains a lot of comments
+// Non-commented version is in /without-comments/main.go
+
+func main() {
+	// You cannot use this syntax.
+	//
+	// feetInMeters is declared
+	//   when the declaration completes,
+	//   (at the end of the whole declaration)
+	//
+	// And, it's not easy to read
+	//
+	// const feetInMeters, feetInYards float64 = 0.3048,
+	//   feetInMeters / 0.9144
+
+	const (
+		feetInMeters = 0.3048
+		feetInYards  = feetInMeters / 0.9144
+
+		// cannot call runtime funcs
+		// feetInYards = math.Round(feetInYards)
+	)
+
+	// Immutable: You cannot assign new values
+	// feetInYards = 0.333333
+
+	arg := os.Args[1]
+
+	feet, _ := strconv.ParseFloat(arg, 64)
+
+	meters := feet * feetInMeters
+	yards := math.Round(feet * feetInYards)
+
+	fmt.Printf("%g feet is %g meters.\n", feet, meters)
+	fmt.Printf("%g feet is %g yards.\n", feet, yards)
+}

10-constants/03-refactor-feet-to-meters/solution/without-comments/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"
+	"math"
+	"os"
+	"strconv"
+)
+
+// I copied the same program here but without comments.
+// So, you can easily read it.
+
+func main() {
+	const (
+		feetInMeters = 0.3048
+		feetInYards  = feetInMeters / 0.9144
+	)
+
+	arg := os.Args[1]
+
+	feet, _ := strconv.ParseFloat(arg, 64)
+
+	meters := feet * feetInMeters
+	yards := math.Round(feet * feetInYards)
+
+	fmt.Printf("%g feet is %g meters.\n", feet, meters)
+	fmt.Printf("%g feet is %g yards.\n", feet, yards)
+}