forked from steger/pr3-ws202627
Merge remote-tracking branch 'upstream/main'
# Conflicts: # go/01-basics/calculator.go # go/01-basics/inventory.go # go/02-next-level/02-struct-embedding.go
ChaosLL1337
commit
e17734dab4
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@ -1,3 +1,3 @@
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module gitty.informatik.th-mannheim.de/steger/pr3-sose2026/go/00-hello-world/hello-world
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module gitty.informatik.th-mannheim.de/steger/pr3-ws202526/go/00-hello-world/hello-world
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go 1.26.0
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@ -13,33 +13,23 @@ func main() {
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exit = "exit"
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)
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//TODO: implement according to README.md
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fmt.Println("Welcome to the Simple Calculator!")
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for {
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var operation string
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fmt.Print("\nEnter operation (add, subtract, multiply, divide, exit): ")
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fmt.Scan(&operation)
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//the following code just demonstrates how to use fmt.Scan
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if operation == exit {
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fmt.Println("Goodbye!")
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break
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}
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var str string
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fmt.Print("Please enter a string: ")
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fmt.Scan(&str)
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var num1, num2 float64
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fmt.Print("Enter the first number: ")
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fmt.Scan(&num1)
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fmt.Print("Enter the second number: ")
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fmt.Scan(&num2)
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var x float64
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fmt.Print("Please enter a float: ")
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fmt.Scan(&x)
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fmt.Printf("You entered '%s' and %f\n", str, x)
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switch operation {
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case add:
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fmt.Printf("Result: %.2f\n", num1+num2)
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@ -1,15 +1,20 @@
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package main
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package main
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import "fmt"
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type Category int
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const (
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Electronics Category = iota
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Groceries
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Clothes
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import (
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"fmt"
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)
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// a new type named Category that can hold integer values
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type Category int
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// The go equivalent of an enum that enumerates different named Categories
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const (
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Electronics Category = iota //0
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Groceries //1
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Clothes //2
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)
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// implementation of the fmt.Stringer interface. In that way, Categories can be printed using the fmt.Print* functions
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func (c Category) String() string {
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switch c {
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case Electronics:
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@ -23,99 +28,93 @@ func (c Category) String() string {
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}
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}
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// Struct for product details
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type Product struct {
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Name string
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Price float64
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Quantity int
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Category string //TODO: use enum instead
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Category Category
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}
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func addProduct(inventory *[]Product, name string, price float64, quantity int, category string) {
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//TODO: implement
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// Add a new product to the inventory
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func addProduct(inventory *[]Product, name string, price float64, quantity int, category Category) {
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// Check if the product already exists in the inventory
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for _, product := range *inventory {
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if product.Name == name {
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fmt.Println("Product already exists.")
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return
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}
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}
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// Add the new product
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*inventory = append(*inventory, Product{
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Name: name,
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Price: price,
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Quantity: quantity,
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Category: category,
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})
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fmt.Printf("Added product: %s\n", name)
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// implementation of the fmt.Stringer interface for printing products
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func (p Product) String() string {
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return fmt.Sprintf("%s (%s, Price: $%.2f, Quantity: %d)", p.Name, p.Category, p.Price, p.Quantity)
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}
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// Remove a product from the inventory
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func removeProduct(inventory *[]Product, name string) {
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//TODO: implement
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for i, product := range *inventory {
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if product.Name == name {
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*inventory = append((*inventory)[:i], (*inventory)[i+1:]...)
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fmt.Printf("Removed product: %s\n", name)
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return
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}
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func addProduct(inventory map[string]Product, name string, price float64, quantity int, category Category) {
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//do not create a new product in case a product with the name already exists
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if _, exists := inventory[name]; exists {
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fmt.Printf("Unable to add new Product %s: Product already exists.\n", name)
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return
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}
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fmt.Println("Product not found.")
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//create a new product...
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p := Product{name, price, quantity, category}
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inventory[name] = p // ...and insert it into the map
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}
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// Update the quantity of a product
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func updateQuantity(inventory *[]Product, name string, newQuantity int) {
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//TODO: implement
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for i, product := range *inventory {
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if product.Name == name {
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(*inventory)[i].Quantity = newQuantity
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fmt.Printf("Updated quantity for %s: New Quantity = %d\n", name, newQuantity)
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return
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}
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}
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fmt.Println("Product not found.")
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func removeProduct(inventory map[string]Product, name string) {
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//no checks required. Does nothing if the product doesn't exist.
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delete(inventory, name)
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}
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// Display the inventory
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func displayInventory(inventory []Product) {
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//TODO: implement
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fmt.Println("Inventory:")
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for _, product := range inventory {
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fmt.Printf("%s - %s (Price: $%.2f, Quantity: %d)\n",
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product.Name, product.Category, product.Price, product.Quantity)
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func updateQuantity(inventory map[string]Product, name string, newQuantity int) {
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p := inventory[name] //read from the map
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p.Quantity = newQuantity //update value
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inventory[name] = p //store back into the map
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}
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func displayInventory(inventory map[string]Product) {
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//Iterate over the inventory
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i := 1
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for _, p := range inventory { //don't care about the key (_), only the value (p) is relevant
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fmt.Printf("%d. %s\n", i, p)
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i++
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}
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}
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func main() {
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// Initialize inventory
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inventory := []Product{
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{Name: "Laptop", Price: 1000, Quantity: 5, Category: "Electronics"},
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{Name: "Apples", Price: 2, Quantity: 50, Category: "Groceries"},
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{Name: "T-shirt", Price: 10, Quantity: 20, Category: "Clothes"},
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{Name: "Laptop", Price: 1000, Quantity: 5, Category: Electronics},
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{Name: "Apples", Price: 2, Quantity: 50, Category: Groceries},
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{Name: "T-shirt", Price: 10, Quantity: 20, Category: Clothes},
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fmt.Println("Welcome to the Inventory Manager!")
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// Store a fixed list of initial product names in an array.
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initialProductNames := [...]string{"Laptop"}
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// Convert the array into a slice so the inventory can grow or shrink dynamically.
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productNames := initialProductNames[:]
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productNames = append(productNames, "Apples", "T-shirt")
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// Use a map to associate product names with details like quantity, price, and category.
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prices := []float64{1000.0, 2.0, 10.0}
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quantities := []int{5, 50, 20}
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categories := []Category{Electronics, Groceries, Clothes}
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inventory := make(map[string]Product)
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for i, name := range productNames {
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inventory[name] = Product{name, prices[i], quantities[i], categories[i]}
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}
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// Display initial inventory
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fmt.Println("\nInitial Inventory:")
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displayInventory(inventory)
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// Add a new product
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addProduct(&inventory, "Phone", 800, 10, "Electronics")
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addProduct(&inventory, "Phone", 800, 10, Electronics)
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fmt.Println("\nAdding a new product: Phone (Electronics, Price: $800, Quantity: 10)")
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addProduct(inventory, "Phone", 800, 10, Electronics)
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// Display updated inventory
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fmt.Println("\nUpdated Inventory:")
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displayInventory(inventory)
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// Update the quantity of an existing product
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updateQuantity(&inventory, "Apples", 30)
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fmt.Println("\nUpdating quantity for Apples: New Quantity = 30")
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updateQuantity(inventory, "Apples", 30)
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// Remove a product
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removeProduct(&inventory, "T-shirt")
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fmt.Println("\nRemoving product: T-shirt")
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removeProduct(inventory, "T-shirt")
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// Display final inventory
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fmt.Println("\nFinal Inventory:")
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displayInventory(inventory)
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}
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}
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@ -0,0 +1,26 @@
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package main
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import "fmt"
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type Counter struct {
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value int
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}
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// pointer receiver. The method operates directly on the object c points to
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// Use a pointer receiver whenever the object needs to be modified.
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func (c *Counter) Increment() {
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c.value++
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}
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// value receiver. The method operates on copy of object c. Use a value
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// receiver when the object does not need to be modified in the method.
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func (c Counter) String() string {
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return fmt.Sprintf("Counter value: %d", c.value)
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}
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func main() {
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c := Counter{}
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fmt.Println(c)
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c.Increment()
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fmt.Println(c)
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}
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@ -0,0 +1,66 @@
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package main
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import (
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"fmt"
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"math"
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)
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type geometry interface {
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area() float64
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perim() float64
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}
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type rect struct {
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width, height float64
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}
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// Ensure that rect implements the geometry interface
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var _ geometry = rect{}
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type circle struct {
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radius float64
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}
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// Ensure that circle implements the geometry interface
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var _ geometry = circle{}
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func (r rect) area() float64 {
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return r.width * r.height
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}
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func (r rect) perim() float64 {
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return 2*r.width + 2*r.height
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}
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func (c circle) area() float64 {
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return math.Pi * c.radius * c.radius
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}
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func (c circle) perim() float64 {
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return 2 * math.Pi * c.radius
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}
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//Metods demonstrates how to use an interface
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func measure(g geometry) {
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fmt.Println(g)
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fmt.Println(g.area())
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fmt.Println(g.perim())
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}
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//Method demonstrates casting an interface to a concrete type.
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//Should be avoided in practice whenever possible.
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func detectCircle(g geometry) {
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if c, ok := g.(circle); ok {
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fmt.Println("circle with radius", c.radius)
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}
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}
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func main() {
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r := rect{width: 3, height: 4}
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c := circle{radius: 5}
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measure(r)
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measure(c)
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detectCircle(r)
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detectCircle(c)
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}
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@ -11,12 +11,12 @@ func (p Person) Say() {
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}
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type Student struct {
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Person //struct Person is embedded
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Person //struct Person is embedded
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Semester int
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}
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type Teacher struct {
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Person //struct Person is embedded
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Person //struct Person is embedded
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Subject string
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}
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|
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@ -2,7 +2,10 @@ package main
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import "fmt"
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func SlicesIndex[S []E, E int](s []string, v string) int {
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// a generic function that takes a slice of any type and a value of that type, and returns the index of the value in the slice, or -1 if it is not found.
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// The type parameters S and E are declared in square brackets before the function name, and they can be used in the function signature and body.
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// The constraint comparable means that the type E must support the == operator, which is necessary for comparing the value with the elements of the slice.
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func SlicesIndex[S []E, E comparable](s S, v E) int {
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for i := range s {
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if v == s[i] {
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return i
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@ -11,27 +14,34 @@ func SlicesIndex[S []E, E int](s []string, v string) int {
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return -1
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}
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type List struct {
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head, tail *element
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// represents a linked list of any type T. The type parameter T is used in the definition of List and its methods,
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// and it can be instantiated with any type when we create a List value. The type any is in fact defined as
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// an empty interface. Thanks to duck-typing it can be used to represent any type, but it does not provide any
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// operations on the values of that type.
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type List[T any] struct {
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head, tail *element[T]
|
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}
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|
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type element struct {
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next *element
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val int
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// the generic element of the linked list
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type element[T any] struct {
|
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next *element[T]
|
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val T
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||||
}
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||||
|
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func (lst *List) Push(v int) {
|
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// adds an instance of the generic type to the list
|
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func (lst *List[T]) Push(v T) {
|
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if lst.tail == nil {
|
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lst.head = &element{val: v}
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lst.head = &element[T]{val: v}
|
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lst.tail = lst.head
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} else {
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lst.tail.next = &element{val: v}
|
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lst.tail.next = &element[T]{val: v}
|
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lst.tail = lst.tail.next
|
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}
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}
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|
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func (lst *List) AllElements() []int {
|
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var elems []int
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// returns all elements of the list as a slice of the generic type.
|
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func (lst List[T]) AllElements() []T {
|
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var elems []T
|
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for e := lst.head; e != nil; e = e.next {
|
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elems = append(elems, e.val)
|
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}
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|
|
@ -39,13 +49,21 @@ func (lst *List) AllElements() []int {
|
|||
}
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|
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func main() {
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|
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var s = []string{"foo", "bar", "zoo"}
|
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// The types S and E are explicitly specified as []string and string respectively.
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fmt.Println("index of zoo:", SlicesIndex[[]string, string](s, "zoo"))
|
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|
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fmt.Println("index of zoo:", SlicesIndex(s, "zoo"))
|
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var s2 = []int{2, 4, 5, 6}
|
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// The type E is inferred from the type of the value 4, which is int,
|
||||
// and the type S is inferred from the type of the slice s2, which is []int.
|
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fmt.Println("index of 4: ", SlicesIndex(s2, 4))
|
||||
|
||||
lst := List{}
|
||||
// instantiate a list of float64 elements
|
||||
lst := List[float64]{}
|
||||
lst.Push(10)
|
||||
lst.Push(13)
|
||||
lst.Push(23)
|
||||
lst.Push(23.3)
|
||||
fmt.Println("list:", lst.AllElements())
|
||||
}
|
||||
|
|
|
|||
|
|
@ -6,18 +6,22 @@ import (
|
|||
)
|
||||
|
||||
func main() {
|
||||
f := createFile("/tmp/defer.txt")
|
||||
writeFile(f)
|
||||
closeFile(f)
|
||||
}
|
||||
|
||||
func createFile(p string) *os.File {
|
||||
fmt.Println("creating")
|
||||
f, err := os.Create(p)
|
||||
f, err := os.Create("/tmp/defer.txt")
|
||||
|
||||
// defer the closing of the file until the surrounding function returns.
|
||||
// This ensures that the file will be closed even if there is a panic or an early return in the function.
|
||||
defer closeFile(f)
|
||||
|
||||
if err != nil {
|
||||
panic(err)
|
||||
}
|
||||
return f
|
||||
|
||||
//will not be called in case of a panic before
|
||||
writeFile(f)
|
||||
|
||||
// closeFile will be called here due to the defer-statement, even in case of a panic before.
|
||||
}
|
||||
|
||||
func writeFile(f *os.File) {
|
||||
|
|
@ -27,8 +31,10 @@ func writeFile(f *os.File) {
|
|||
|
||||
func closeFile(f *os.File) {
|
||||
fmt.Println("closing")
|
||||
err := f.Close()
|
||||
|
||||
var err error
|
||||
if f != nil {
|
||||
err = f.Close()
|
||||
}
|
||||
if err != nil {
|
||||
panic(err)
|
||||
}
|
||||
|
|
|
|||
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