Initial commit

10-constants/01-declarations/01-syntax/01-magic-numbers/main.go

@@ -0,0 +1,22 @@
+// 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"
+
+// This program uses magic values
+
+func main() {
+	cm := 100
+	m := cm / 100 // 100 is a magic value
+	fmt.Printf("%dcm is %dm\n", cm, m)
+
+	cm = 200
+	m = cm / 100 // 100 is a magic value
+	fmt.Printf("%dcm is %dm\n", cm, m)
+}

10-constants/01-declarations/01-syntax/02-constants/main.go

@@ -0,0 +1,25 @@
+// 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"
+
+// This program uses a named constant
+// instead of a magic value
+
+func main() {
+	const meters int = 100
+
+	cm := 100
+	m := cm / meters // using a named constant
+	fmt.Printf("%dcm is %dm\n", cm, m)
+
+	cm = 200
+	m = cm / meters // using a named constant
+	fmt.Printf("%dcm is %dm\n", cm, m)
+}

10-constants/01-declarations/01-syntax/03-safety/main.go

@@ -0,0 +1,26 @@
+// 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"
+
+func main() {
+	// Go can't catch the same error at runtime
+	// When you run this, there will be an error:
+	//
+	// panic: runtime error: integer divide by zero
+	n, m := 1, 0
+	fmt.Println(n / m)
+
+	// Go will detect the division by zero error
+	// at compile-time
+	//
+	// const n int = 1
+	// const m int = 0
+	// fmt.Println(n / m)
+}

10-constants/01-declarations/01-syntax/04-rules/01-immutability/main.go

@@ -0,0 +1,16 @@
+// 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() {
+	const max int = 100
+
+	// ERROR: cannot assign to max
+	//        constants are immutable (cannot change)
+	// max = 100
+}

10-constants/01-declarations/01-syntax/04-rules/02-runtime-func/main.go

@@ -0,0 +1,25 @@
+// 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"
+)
+
+func main() {
+	// math.Pow calculates the power of the given number
+	fmt.Println(math.Pow10(2)) // 100
+	fmt.Println(math.Pow10(3)) // 1000
+	fmt.Println(math.Pow10(4)) // 10000
+
+	// ERROR: math.Pow is not a constant
+	//        constants cannot use runtime constructs
+
+	// const max int = math.Pow10(2)
+}

10-constants/01-declarations/01-syntax/04-rules/03-runtime-var/main.go

@@ -0,0 +1,17 @@
+// 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() {
+	n := 2
+
+	// ERROR: n is not a constant
+	// const max int = n
+
+	_ = n
+}

10-constants/01-declarations/01-syntax/04-rules/04-len/main.go

@@ -0,0 +1,21 @@
+// 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"
+
+func main() {
+	// When argument to len is a constant, len can be used
+	// while initializing a constant
+	//
+	// Here, "Hello" is a constant.
+
+	const max int = len("Hello")
+
+	fmt.Println(max)
+}