Merge remote-tracking branch 'upstream/main'

go/01-basics/calculator.go

@@ -5,18 +5,46 @@ import (
 )
 
 func main() {
+	const (
+		add      = "add"
+		subtract = "subtract"
+		multiply = "multiply"
+		divide   = "divide"
+		exit     = "exit"
+	)
 
-	//TODO: implement according to README.md
+	fmt.Println("Welcome to the Simple Calculator!")
+	for {
+		var operation string
+		fmt.Print("\nEnter operation (add, subtract, multiply, divide, exit): ")
+		fmt.Scan(&operation)
 
-	//the following code just demonstrates how to use fmt.Scan
-
-	var str string
-	fmt.Print("Please enter a string: ")
-	fmt.Scan(&str)
-
-	var x float64
-	fmt.Print("Please enter a float: ")
-	fmt.Scan(&x)
-
-	fmt.Printf("You entered '%s' and %f\n", str, x)
+		if operation == exit {
+			fmt.Println("Goodbye!")
+			break
+		}
+
+		var num1, num2 float64
+		fmt.Print("Enter the first number: ")
+		fmt.Scan(&num1)
+		fmt.Print("Enter the second number: ")
+		fmt.Scan(&num2)
+
+		switch operation {
+		case add:
+			fmt.Printf("Result: %.2f\n", num1+num2)
+		case subtract:
+			fmt.Printf("Result: %.2f\n", num1-num2)
+		case multiply:
+			fmt.Printf("Result: %.2f\n", num1*num2)
+		case divide:
+			if num2 == 0 {
+				fmt.Println("Error: Division by zero is not allowed!")
+			} else {
+				fmt.Printf("Result: %.2f\n", num1/num2)
+			}
+		default:
+			fmt.Println("Invalid operation. Please try again.")
+		}
+	}
 }

go/01-basics/slice.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"runtime"
+)
+
+func main() {
+	//create an array with a lot of data
+	massiveData := make([]int, 1_000_000)
+	for i := range massiveData {
+		massiveData[i] = i
+	}
+
+	// Task: Extract the first 8 elements safely
+
+	//1. attempt: use the slice operator
+	//smallSlice := massiveData[:8]
+	// consequence -> smallSlice and massiveData point to the same underlying array.
+	// Therefore, setting massiveData to nil is not sufficient to release that big array.
+
+	//2. attempt: create a new slice (with a new underlying array) and copy data
+	smallSlice := make([]int, 8)
+	copy(smallSlice, massiveData[:8])
+
+	massiveData = nil //don't use massive data anymore: Underlying array shall be freed.
+	runtime.GC()      //run the garbage collector to make sure that all unused data is actually freed
+
+	//cap(smallSlice) should be 8 or similar, but not close to 1_000_000. The majority of the data should have been released by now
+	fmt.Printf("Small Slice: %v, Len: %d, Cap: %d\n", smallSlice, len(smallSlice), cap(smallSlice))
+}