add: array exercises

14-arrays/exercises/09-currency-converter/main.go

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+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Currency Converter
+//
+//   In this exercise, you're going to display currency exchange ratios
+//   against USD.
+//
+//   1. Declare a few constants with iota. They're going to be the keys
+//      of the array.
+//
+//   2. Create an array that contains the conversion ratios.
+//
+//      You should use keyed elements and the contants you've declared before.
+//
+//   3. Get the USD amount to be converted from the command line.
+//
+//   4. Handle the error cases for missing or invalid input.
+//
+//   5. Print the exchange ratios.
+//
+// EXPECTED OUTPUT
+//   go run main.go
+//     Please provide the amount to be converted.
+//
+//   go run main.go invalid
+//     Invalid amount. It should be a number.
+//
+//   go run main.go 10.5
+//     10.50 USD is 9.24 EUR
+//     10.50 USD is 8.19 GBP
+//     10.50 USD is 1186.71 JPY
+//
+//   go run main.go 1
+//     1.00 USD is 0.88 EUR
+//     1.00 USD is 0.78 GBP
+//     1.00 USD is 113.02 JPY
+// ---------------------------------------------------------
+
+func main() {
+}

14-arrays/exercises/09-currency-converter/solution/main.go

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+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	const (
+		EUR = iota
+		GBP
+		JPY
+	)
+
+	rates := [...]float64{
+		EUR: 0.88,
+		GBP: 0.78,
+		JPY: 113.02,
+	}
+
+	args := os.Args[1:]
+	if len(args) != 1 {
+		fmt.Println("Please provide the amount to be converted.")
+		return
+	}
+
+	amount, err := strconv.ParseFloat(args[0], 64)
+	if err != nil {
+		fmt.Println("Invalid amount. It should be a number.")
+		return
+	}
+
+	fmt.Printf("%.2f USD is %.2f EUR\n", amount, rates[EUR]*amount)
+	fmt.Printf("%.2f USD is %.2f GBP\n", amount, rates[GBP]*amount)
+	fmt.Printf("%.2f USD is %.2f JPY\n", amount, rates[JPY]*amount)
+}