add: slices - first part

16-slices/01-slices-vs-arrays/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"
+
+func main() {
+	{
+		// its length is part of its type
+		var nums [5]int
+		fmt.Printf("nums array: %#v\n", nums)
+	}
+
+	{
+		// its length is not part of its type
+		var nums []int
+		fmt.Printf("nums slice: %#v\n", nums)
+
+		fmt.Printf("len(nums) : %d\n", len(nums))
+
+		// won't work: the slice is nil.
+		// fmt.Printf("nums[0]: %d\n", nums[0])
+		// fmt.Printf("nums[1]: %d\n", nums[1])
+	}
+}

16-slices/02-slices-vs-arrays/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"
+
+func main() {
+	var array [2]int
+
+	// zero value of an array is zero-valued elements
+	fmt.Printf("array       : %#v\n", array)
+
+	// nope: arrays are fixed length
+	// array[2] = 0
+
+	var slice []int
+
+	// zero value of a slice is nil
+	fmt.Println("slice == nil?", slice == nil)
+
+	// nope: they don't exist:
+	// _ = slice[0]
+	// _ = slice[1]
+
+	// len function still works though
+	fmt.Println("len(slice)  :", len(slice))
+
+	// array's length is part of its type
+	fmt.Printf("array's type: %T\n", array)
+
+	// whereas, slice's length isn't part of its type
+	fmt.Printf("slice's type: %T\n", slice)
+}

16-slices/03-slices-vs-arrays-examples/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"
+
+// STORY:
+// You want to list the books and games you have
+
+func main() {
+	var books [5]string
+	books[0] = "dracula"
+	books[1] = "1984"
+	books[2] = "island"
+
+	newBooks := [5]string{"ulysses", "fire"}
+	if books == newBooks {
+	}
+	books = newBooks
+
+	games := []string{"kokemon", "sims"}
+	newGames := []string{"pacman", "doom", "pong"}
+	newGames = games
+	games = nil
+	games = []string{}
+
+	var ok string
+	for i, game := range games {
+		if game != newGames[i] {
+			ok = "not "
+			break
+		}
+	}
+
+	if len(games) != len(newGames) {
+		ok = "not "
+	}
+
+	fmt.Printf("games and newGames are %sequal\n\n", ok)
+
+	fmt.Printf("books         : %#v\n", books)
+	fmt.Printf("new books     : %#v\n", newBooks)
+	fmt.Printf("games         : %T\n", games)
+	fmt.Printf("new games     : %#v\n", newGames)
+	fmt.Printf("games's length: %d\n", len(games))
+	fmt.Printf("games's nil   : %t\n", games == nil)
+}

16-slices/04-slices-vs-arrays-unique-nums/01-with-arrays/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"
+	"math/rand"
+	"time"
+)
+
+func main() {
+	rand.Seed(time.Now().UnixNano())
+
+	const max = 5
+	var uniques [max]int
+
+	// It's harder to make a program dynamic using arrays
+	// max, _ := strconv.Atoi(os.Args[1])
+	// var uniques [10]int
+
+loop:
+	for found := 0; found < max; {
+		n := rand.Intn(max) + 1
+		fmt.Print(n, " ")
+
+		for _, u := range uniques {
+			if u == n {
+				continue loop
+			}
+		}
+
+		uniques[found] = n
+		found++
+	}
+
+	fmt.Println("\n\nuniques:", uniques)
+}

16-slices/04-slices-vs-arrays-unique-nums/02-with-slices/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"
+	"math/rand"
+	"os"
+	"sort"
+	"strconv"
+	"time"
+)
+
+func main() {
+	rand.Seed(time.Now().UnixNano())
+
+	max, _ := strconv.Atoi(os.Args[1])
+
+	// declare an uninitialized nil slice
+	var uniques []int
+
+loop:
+	// you can still use the len function on a nil slice
+	for len(uniques) < max {
+		n := rand.Intn(max) + 1
+		fmt.Print(n, " ")
+
+		for _, u := range uniques {
+			if u == n {
+				continue loop
+			}
+		}
+
+		// append can add new elements the slice
+		uniques = append(uniques, n)
+
+		// a slice doesn't contain any elements from the beginning
+		// uniques[found] = n
+		// found++
+	}
+
+	fmt.Println("\n\nuniques:", uniques)
+	fmt.Println("\nlength of uniques:", len(uniques))
+
+	sort.Ints(uniques)
+	fmt.Println("\nsorted:", uniques)
+
+	nums := [5]int{5, 4, 3, 2, 1}
+	sort.Ints(nums[:])
+	fmt.Println("\nnums:", nums)
+}

16-slices/README.md

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+# WARNING
+
+For the code in this section, you should install my prettyslice library.
+
+## STEPS
+1. Open your command-line
+2. Type: `go get -u github.com/inancgumus/prettyslice`
+3. That's all.

16-slices/questions/1-slices-vs-arrays.md

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+# Slices vs Arrays Quiz
+
+## Why you want to use a slice instead of an array?
+1. I like arrays more
+2. I want to create a dynamic collection, so I need an array
+3. A slice's length is dynamic, so I can create dynamic collections *CORRECT*
+
+
+## When does the length of a slice is determined?
+1. At compile-time
+2. In runtime *CORRECT*
+3. When a program terminates
+
+> **2:** A slice's length is not a part of its type. So its length can change at runtime.
+
+
+## Which function call below is correct?
+```go
+// Let's say there's a function like this.
+func sort(nums []int) {
+    // ...
+}
+```
+1. sort([...]int{3, 1, 6})
+2. sort([]int32{3, 1, 6})
+3. sort([]int{3, 1, 6}) *CORRECT*
+
+> **1:** You can't call the sort function using an array. It expects an int slice.
+> 
+> **2:** You can't call the sort function using an int32 slice. It expects an int slice.
+> 
+> **3:** That's right! You can pass an int slice to the sort function.
+
+
+## What is the zero value of this slice?
+```go
+var tasks []string
+```
+1. 0
+2. 1
+3. nil *CORRECT*
+4. unknown
+
+> **3:** This is a nil slice. Unlike an array, a slice's zero value is nil.
+
+
+## What does this code print?
+```go
+var tasks []string
+fmt.Println(len(tasks))
+```
+
+1. 0 *CORRECT*
+2. 1
+3. nil
+4. It doesn't work.
+
+> **1:** Yes, you can use the len function on a nil slice. It returns 0 because the slice doesn't contain any elements yet.
+
+
+## What does this code print?
+```go
+var tasks []string
+fmt.Println(tasks[0])
+```
+
+1. 0
+2. 1
+3. nil
+4. It doesn't work. *CORRECT*
+
+> **4:** You can't get an element that does not exist. A nil slice does not contain any elements.
+
+
+## Which declaration below is a correct slice declaration?
+1. [...]int{}
+2. [2]string{"hello", "world"}
+3. []string{"hello", "world"} *CORRECT*
+4. string[2]{"hello", world"}
+
+
+## This code doesn't work, why?
+```go
+colors := []string{"red", "blue", "green"}
+tones := []string{"dark", "light"}
+
+if colors == tones {
+    // ...
+}
+```
+
+1. The slices have different lengths
+2. If statement doesn't contain any statements
+3. Slices cannot be compared *CORRECT*
+
+> **3:** That's right! A slice value can only be compared to a nil value.
+
+
+## What is the length of this slice?
+```go
+[]uint64{}
+```
+
+1. 64
+2. 1
+3. 0 *CORRECT*
+4. Error
+
+> **3:** That's right. This is an empty slice, it doesn't contain any elements.
+
+
+## What is the length of this slice?
+```go
+[]string{"i'm", "going", "to", "stay", "\"here\""}
+```
+
+1. 0
+2. 1
+3. 2
+4. 3
+5. 4
+6. 5 *CORRECT*

16-slices/questions/README.md

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+# Slice Quizzes
+
+* [Slices vs Arrays](1-slices-vs-arrays.md)