97 lines
2.7 KiB
Go
97 lines
2.7 KiB
Go
// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import "fmt"
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type computer struct {
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brand string
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}
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func main() {
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// create a nil pointer with the type of pointer to a computer
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var null *computer
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// compare the pointer variable to a nil value
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if null == nil {
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// , and say it's nil
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fmt.Println("null computer is nil")
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}
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// create an apple computer by putting its address to a pointer variable
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apple := &computer{brand: "apple"}
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// put the apple into a new pointer variable
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newApple := apple
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// compare the apples: if they are equal
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if apple == newApple {
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// say so and print their addresses
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fmt.Printf("apples are equal : apple: %p newApple: %p\n",
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apple, newApple)
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}
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// create a sony computer by putting its address to a new pointer variable
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sony := &computer{brand: "sony"}
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// compare apple to sony, if they are not equal
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if apple != sony {
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// say so and print their addresses
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fmt.Printf("apple and sony are inequal: apple: %p sony: %p\n",
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apple, sony)
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}
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// put apple's value into a new ordinary variable
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appleVal := *apple
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// print apple pointer variable's address, and the address it points to
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// and, print the new variable's addresses as well
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fmt.Printf("apple : %p %p\n", &apple, apple)
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fmt.Printf("appleVal : %p\n", &appleVal)
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// compare the value that is pointed by the apple and the new variable
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if *apple == appleVal {
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// if they are equal say so
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fmt.Println("apple and appleVal are equal")
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// print the values:
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// the value that is pointed by the apple and the new variable
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fmt.Printf("apple : %+v — appleVal: %+v\n",
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*apple, appleVal)
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}
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// change sony's brand to hp using the func
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change(sony, "hp")
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// print sony's brand
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fmt.Printf("sony : %s\n", sony.brand)
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// print the returned value
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fmt.Printf("appleVal : %+v\n", valueOf(apple))
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// and call the func 3 times and print the returned values' addresses
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fmt.Printf("dell's address : %p\n", newComputer("dell"))
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fmt.Printf("lenovo's address : %p\n", newComputer("lenovo"))
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fmt.Printf("acer's address : %p\n", newComputer("acer"))
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}
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// create a new function: change
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// the func can change the given computer's brand to another brand
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func change(c *computer, brand string) {
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c.brand = brand
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}
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// write a func that returns the value that is pointed by the given *computer
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func valueOf(c *computer) computer {
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return *c
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}
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// write a new constructor func that returns a pointer to a computer
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func newComputer(brand string) *computer {
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return &computer{brand: brand}
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}
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