add: maps first four lectures

x-tba/maps/01-english-dict-slice/main.go

@@ -0,0 +1,35 @@
+// 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"
+	"os"
+)
+
+func main() {
+	args := os.Args[1:]
+	if len(args) != 1 {
+		fmt.Println("[english word] -> [turkish word]")
+		return
+	}
+	query := args[0]
+
+	english := []string{"good", "great", "perfect"}
+	turkish := []string{"iyi", "harika", "mükemmel"}
+
+	// O(n) -> Inefficient: Depends on 'n'.
+	for i, w := range english {
+		if query == w {
+			fmt.Printf("%q means %q\n", w, turkish[i])
+			return
+		}
+	}
+
+	fmt.Printf("%q not found\n", query)
+}

x-tba/maps/02-english-dict-map/main.go

@@ -0,0 +1,52 @@
+// 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() {
+	/*
+		#1: Nil Map: Read-Only
+	*/
+	var dict map[string]string
+	fmt.Printf("Zero-value of a map: %#v\n", dict)
+
+	/*
+		#5: You cannot assign to a nil map.
+	*/
+	// dict["up"] = "yukarı"
+	// dict["down"] = "aşağı"
+
+	/*
+		#2: Map retrieval is O(1) — on average.
+	*/
+	key := "good"
+	//
+	// #4: you can use an uninitialized map without checking it is nil
+	//
+	// if dict != nil {
+	value := dict[key]
+	fmt.Printf("%q means %#v\n", key, value)
+	// }
+
+	/*
+		#3: Cannot use non-comparable types as map key types
+	*/
+	// var broken map[[]int]int
+	// var broken map[map[int]string]bool
+	//
+	// A map can only be compared to nil value
+	// _ = dict == nil
+
+	/*
+		#1 Step 2
+	*/
+	fmt.Printf("The dictionary contains %d words.\n", len(dict))
+}

x-tba/maps/03-english-dict-map-populate/main.go

@@ -0,0 +1,119 @@
+// 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"
+	"os"
+)
+
+func main() {
+	/*
+		#2—A: Get the key from CLI
+	*/
+	args := os.Args[1:]
+	if len(args) != 1 {
+		fmt.Println("[english word] -> [turkish word]")
+		return
+	}
+	query := args[0]
+
+	/*
+		#1: Empty Map Literal
+	*/
+	// dict := map[string]string{}
+
+	/*
+		#3: Map Literal
+		Creates, initializes and returns a new map
+		with the given key-value pairs
+	*/
+	dict := map[string]string{
+		"good":    "kötü",
+		"great":   "harika",
+		"perfect": "mükemmel",
+		/*
+			#4: keys and values should be the same type
+				(key and value types do not need to be the same)
+		*/
+		// 42: "forty two",
+		// "forty two": 42,
+	}
+
+	// you can only add new pairs to an initialized map
+	dict["up"] = "yukarı"  // adds a new pair
+	dict["down"] = "aşağı" // adds a new pair
+	dict["good"] = "iyi"   // #5: overwrites the value at the key: "good"
+	dict["mistake"] = ""   // #8: a key with a zero-value
+
+	// you can query an uninitialized map for its length
+	fmt.Printf("The dictionary contains %d words.\n", len(dict))
+
+	/*
+		#6: getting values from a map using keys directly
+	*/
+	// fmt.Println("good      -> ", dict["good"])
+	// fmt.Println("great     -> ", dict["great"])
+	// fmt.Println("perfect   -> ", dict["perfect"])
+
+	/*
+		#11: looping over a map might be a sign for a design mistake
+			 in your software.
+
+			 (it prints unordered output)
+	*/
+	// for k, v := range dict {
+	// 	fmt.Printf("%q means %#v\n", k, v)
+	// }
+
+	/*
+		#12: printing a map (ordered output since Go 1.12)
+	*/
+	// fmt.Printf("%#v\n", dict)
+
+	/*
+		#13: compare a map using its printed output
+			 (handy when testing)
+	*/
+	// copied := map[string]string{"up": "yukarı", "down": "aşağı",
+	// 	"mistake": "", "good": "iyi", "great": "harika",
+	// 	"perfect": "mükemmel"}
+
+	// first := fmt.Sprintf("%s", dict)
+	// second := fmt.Sprintf("%s", copied)
+
+	// if first == second {
+	// 	fmt.Println("Maps are equal")
+	// }
+
+	/*
+		#2—B: retrieve values by key - O(1) efficiency
+			(even from an uninitialized map)
+	*/
+	// value := dict[query]
+
+	/*
+		#7: check for non-existing key using zero-value
+	*/
+	// if value == "" {}
+
+	/*
+		#9: check for non-existing key: with comma, ok
+	*/
+	// value, ok := dict[query]
+	// if !ok {}
+
+	/*
+		#10: comma ok in a short if
+	*/
+	if value, ok := dict[query]; ok {
+		fmt.Printf("%q means %#v\n", query, value)
+		return
+	}
+	fmt.Printf("%q not found.\n", query)
+}

x-tba/maps/04-internals-cloning/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"
+	"os"
+)
+
+func main() {
+	args := os.Args[1:]
+	if len(args) != 1 {
+		fmt.Println("[english word] -> [turkish word]")
+		return
+	}
+	query := args[0]
+
+	dict := map[string]string{
+		"good":    "iyi",
+		"great":   "harika",
+		"perfect": "mükemmel",
+
+		// #5: this overwrites the mükemmel in the turkish map
+		"awesome": "mükemmel",
+	}
+
+	// #1: map value is a pointer to a real map in the memory
+	// turkish := dict
+	// turkish["good"] = "güzel"
+	// dict["great"] = "kusursuz"
+
+	// #6: delete can delete a pair from a map
+	delete(dict, "awesome")
+
+	// #7: no-op
+	delete(dict, "awesome")
+	delete(dict, "notexisting")
+
+	// #8: destroying a map completely (false)
+	// dict = nil
+
+	// #9: destroying a map completely (true)
+	//     replaces the whole loop with a single instruction:
+	//     "call runtime.mapclear()"
+	for k := range dict {
+		delete(dict, k)
+	}
+
+	// #2: make initializes a new map value and returns a pointer to it
+	// turkish := make(map[string]string)
+
+	// #3: make(T, hint) => hint is an advice for initing a large enough map
+	turkish := make(map[string]string, len(dict))
+	for k, v := range dict {
+		turkish[v] = k
+	}
+
+	// #4: add turkish dictionary
+	// fmt.Printf("english: %q\nturkish: %q\n", dict, turkish)
+
+	if value, ok := dict[query]; ok {
+		fmt.Printf("%q means %#v\n", query, value)
+		return
+	}
+
+	if value, ok := turkish[query]; ok {
+		fmt.Printf("%q means %#v\n", query, value)
+		return
+	}
+
+	fmt.Printf("%q not found.\n", query)
+}

x-tba/maps/README.md

@@ -1 +0,0 @@
-This section is in progress. I'm working hard to update the course all the time. Hold on!