add: arrays

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

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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"
+
+// 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)
+}