add: arrays

14-arrays/11-keyed-elements/01-unkeyed/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"
+
+func main() {
+	rates := [3]float64{
+		0.5,
+		2.5,
+		1.5,
+	}
+
+	fmt.Println(rates)
+}

14-arrays/11-keyed-elements/02-keyed/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"
+
+func main() {
+	rates := [3]float64{
+		0: 0.5, // index: 0
+		1: 2.5, // index: 1
+		2: 1.5, // index: 2
+	}
+
+	fmt.Println(rates)
+
+	// above array literal equals to this:
+	//
+	// rates := [3]float64{
+	// 	0.5,
+	// 	2.5,
+	// 	1.5,
+	// }
+}

14-arrays/11-keyed-elements/03-keyed-order/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"
+
+func main() {
+	rates := [3]float64{
+		1: 2.5, // index: 1
+		0: 0.5, // index: 0
+		2: 1.5, // index: 2
+	}
+
+	fmt.Println(rates)
+
+	// above array literal equals to this:
+	//
+	// rates := [3]float64{
+	// 	0.5,
+	// 	2.5,
+	// 	1.5,
+	// }
+}

14-arrays/11-keyed-elements/04-keyed-auto-initialize/main.go

@@ -0,0 +1,28 @@
+// 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() {
+	rates := [3]float64{
+		// index 0 empty
+		// index 1 empty
+		2: 1.5, // index: 2
+	}
+
+	fmt.Println(rates)
+
+	// above array literal equals to this:
+	//
+	// rates := [3]float64{
+	// 	0.,
+	// 	0.,
+	// 	1.5,
+	// }
+}

14-arrays/11-keyed-elements/05-keyed-auto-initialize-ellipsis/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"
+
+func main() {
+	// ellipsis (...) below calculates the length of the
+	// array automatically
+	rates := [...]float64{
+		// index 0 empty
+		// index 1 empty
+		// index 2 empty
+		// index 3 empty
+		// index 4 empty
+		5: 1.5, // index: 5
+	}
+
+	fmt.Println(rates)
+
+	// above array literal equals to this:
+	//
+	// rates := [6]float64{
+	// 	0.,
+	// 	0.,
+	// 	0.,
+	// 	0.,
+	// 	0.,
+	// 	1.5,
+	// }
+}

14-arrays/11-keyed-elements/06-keyed-and-unkeyed/main.go

@@ -0,0 +1,34 @@
+// 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() {
+	rates := [...]float64{
+		// index 1 to 4 empty
+
+		5:   1.5, // index: 5
+		2.5, //      index: 6
+		0:   0.5, // index: 0
+	}
+
+	fmt.Println(rates)
+
+	// above array literal equals to this:
+	//
+	// rates := [7]float64{
+	// 	0.5,
+	// 	0.,
+	// 	0.,
+	// 	0.,
+	// 	0.,
+	// 	1.5,
+	//  2.5,
+	// }
+}

14-arrays/11-keyed-elements/07-xratio-example/01-without-keys/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() {
+	rates := [...]float64{
+		25.5,  // ethereum
+		120.5, // wanchain
+	}
+
+	// uses magic values - not good
+	fmt.Printf("1 BTC is %g ETH\n", rates[0])
+	fmt.Printf("1 BTC is %g WAN\n", rates[1])
+}

14-arrays/11-keyed-elements/07-xratio-example/02-with-keys/main.go

@@ -0,0 +1,38 @@
+// 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"
+
+// REFACTORED VERSION
+// It uses well-defined names instead of magic numbers.
+// Thanks to the keyed elements and constants.
+
+func main() {
+	const (
+		ETH = 9 - iota
+		WAN
+		ICX
+		// you can add more cryptocurrencies here
+		// watch out the -1 index though!
+	)
+
+	rates := [...]float64{
+		ETH: 25.5,
+		WAN: 120.5,
+		ICX: 20,
+		// you can add more cryptocurrencies here
+	}
+
+	// uses well-defined names (ETH, WAN, ...) - good
+	fmt.Printf("1 BTC is %g ETH\n", rates[ETH])
+	fmt.Printf("1 BTC is %g WAN\n", rates[WAN])
+	fmt.Printf("1 BTC is %g ICX\n", rates[ICX])
+
+	fmt.Printf("%#v\n", rates)
+}