Golang Slices and Maps

Rajeev Kumar Singh · Rajeev Kumar Singh · commit 7e30b32d6ec2 · 2018-03-20T12:41:07.000+05:30
diff --git a/Readme.md b/Readme.md
@@ -10,4 +10,8 @@
 
 5. [Golang Control Flow Statements: If, Switch and For](https://www.callicoder.com/golang-control-flow/)
 
-6. [Working with Arrays in Golang](https://www.callicoder.com/golang-arrays/)
+6. [Working with Arrays in Golang](https://www.callicoder.com/golang-arrays/)
+
+7. [Introduction to Slices in Golang](https://www.callicoder.com/golang-slices/)
+
+8. [Golang Maps by Example](https://www.callicoder.com/golang-maps/)
diff --git a/tutorial7-slices/slice_append.go b/tutorial7-slices/slice_append.go
@@ -0,0 +1,15 @@
+package main
+
+import "fmt"
+
+func main() {
+	var slice1 = []string{"C", "C++", "Java"}
+	var slice2 = append(slice1, "Python", "Ruby", "Go")
+
+	fmt.Printf("slice1 = %v, len = %d, cap = %d\n", slice1, len(slice1), cap(slice1))
+	fmt.Printf("slice2 = %v, len = %d, cap = %d\n", slice2, len(slice2), cap(slice2))
+
+	slice1[0] = "C#"
+	fmt.Println("\nslice1 = ", slice1)
+	fmt.Println("slice2 = ", slice2)
+}
diff --git a/tutorial7-slices/slice_append_capacity.go b/tutorial7-slices/slice_append_capacity.go
@@ -0,0 +1,17 @@
+package main
+
+import "fmt"
+
+func main() {
+	var slice1 = make([]string, 3, 10)
+	copy(slice1, []string{"C", "C++", "Java"})
+
+	var slice2 = append(slice1, "Python", "Ruby", "Go")
+
+	fmt.Printf("slice1 = %v, len = %d, cap = %d\n", slice1, len(slice1), cap(slice1))
+	fmt.Printf("slice2 = %v, len = %d, cap = %d\n", slice2, len(slice2), cap(slice2))
+
+	slice1[0] = "C#"
+	fmt.Println("\nslice1 = ", slice1)
+	fmt.Println("slice2 = ", slice2)
+}
diff --git a/tutorial7-slices/slice_append_nil.go b/tutorial7-slices/slice_append_nil.go
@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	var s []string
+
+	// Appending to a nil slice
+	s = append(s, "Cat", "Dog", "Lion", "Tiger")
+
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+}
diff --git a/tutorial7-slices/slice_append_to_another_slice.go b/tutorial7-slices/slice_append_to_another_slice.go
@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+func main() {
+	var slice1 = []string{"Jack", "John", "Peter"}
+	var slice2 = []string{"Bill", "Mark", "Steve"}
+
+	var slice3 = append(slice1, slice2...)
+
+	fmt.Println("slice1 = ", slice1)
+	fmt.Println("slice2 = ", slice2)
+	fmt.Println("After appending slice1 & slice2 = ", slice3)
+}
diff --git a/tutorial7-slices/slice_capacity_extend.go b/tutorial7-slices/slice_capacity_extend.go
@@ -0,0 +1,21 @@
+package main
+
+import "fmt"
+
+func main() {
+	var s = []int{10, 20, 30, 40, 50, 60, 70, 80, 90, 100}
+	fmt.Println("Original Slice")
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+
+	s = s[1:5]
+	fmt.Println("\nAfter slicing from index 1 to 5")
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+
+	s = s[:8]
+	fmt.Println("\nAfter extending the length")
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+
+	s = s[2:]
+	fmt.Println("\nAfter dropping the first two elements")
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+}
diff --git a/tutorial7-slices/slice_copy.go b/tutorial7-slices/slice_copy.go
@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+func main() {
+	var src = []string{"Sublime", "VSCode", "IntelliJ", "Eclipse"}
+	var dest = make([]string, 2)
+
+	var numElementsCopied = copy(dest, src)
+
+	fmt.Println("src = ", src)
+	fmt.Println("dest = ", dest)
+	fmt.Println("Number of elements copied from src to dest = ", numElementsCopied)
+}
diff --git a/tutorial7-slices/slice_defaults.go b/tutorial7-slices/slice_defaults.go
@@ -0,0 +1,18 @@
+package main
+
+import "fmt"
+
+func main() {
+	var a = [5]string{"C", "C++", "Java", "Python", "Go"}
+
+	var slice1 = a[1:4]
+	var slice2 = a[:3]
+	var slice3 = a[2:]
+	var slice4 = a[:]
+
+	fmt.Println("Array a = ", a)
+	fmt.Println("slice1 = ", slice1)
+	fmt.Println("slice2 = ", slice2)
+	fmt.Println("slice3 = ", slice3)
+	fmt.Println("slice4 = ", slice4)
+}
diff --git a/tutorial7-slices/slice_from_array.go b/tutorial7-slices/slice_from_array.go
@@ -0,0 +1,13 @@
+package main
+
+import "fmt"
+
+func main() {
+	var a = [5]string{"Alpha", "Beta", "Gamma", "Delta", "Epsilon"}
+
+	// Creating a slice from the array
+	var s []string = a[1:4]
+
+	fmt.Println("Array a = ", a)
+	fmt.Println("Slice s = ", s)
+}
diff --git a/tutorial7-slices/slice_length_capacity.go b/tutorial7-slices/slice_length_capacity.go
@@ -0,0 +1,10 @@
+package main
+
+import "fmt"
+
+func main() {
+	var a = [6]int{10, 20, 30, 40, 50, 60}
+	var s = a[1:4]
+
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+}
diff --git a/tutorial7-slices/slice_literal.go b/tutorial7-slices/slice_literal.go
@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+func main() {
+	// Creating a slice using a slice literal
+	var s = []int{3, 5, 7, 9, 11, 13, 17} // Creates an array, and returns a slice reference to the array
+
+	// Short hand declaration
+	t := []int{2, 4, 8, 16, 32, 64}
+
+	fmt.Println("s = ", s)
+	fmt.Println("t = ", t)
+}
diff --git a/tutorial7-slices/slice_make.go b/tutorial7-slices/slice_make.go
@@ -0,0 +1,9 @@
+package main
+
+import "fmt"
+
+func main() {
+	// Creates an array of size 10, slices it till index 5, and returns the slice reference
+	var s = make([]int, 5, 10)
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+}
diff --git a/tutorial7-slices/slice_make_default_capacity.go b/tutorial7-slices/slice_make_default_capacity.go
@@ -0,0 +1,9 @@
+package main
+
+import "fmt"
+
+func main() {
+	// Creates an array of size 5, and returns a slice reference to it
+	var s = make([]int, 5)
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+}
diff --git a/tutorial7-slices/slice_modify.go b/tutorial7-slices/slice_modify.go
@@ -0,0 +1,26 @@
+package main
+
+import "fmt"
+
+func main() {
+	var a = [7]string{"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"}
+
+	var slice1 = a[1:]
+	var slice2 = a[3:]
+
+	fmt.Println("------- Before Modifications -------")
+	fmt.Println("a  = ", a)
+	fmt.Println("slice1 = ", slice1)
+	fmt.Println("slice2 = ", slice2)
+
+	slice1[0] = "TUE"
+	slice1[1] = "WED"
+	slice1[2] = "THU"
+
+	slice2[1] = "FRIDAY"
+
+	fmt.Println("\n-------- After Modifications --------")
+	fmt.Println("a  = ", a)
+	fmt.Println("slice1 = ", slice1)
+	fmt.Println("slice2 = ", slice2)
+}
diff --git a/tutorial7-slices/slice_of_slices.go b/tutorial7-slices/slice_of_slices.go
@@ -0,0 +1,15 @@
+package main
+
+import "fmt"
+
+func main() {
+	var s = [][]string{
+		{"James Smith", "United States"},
+		{"Maria Gracia", "England"},
+		{"Sarah Johnson", "France"},
+	}
+
+	fmt.Println("Slice s = ", s)
+	fmt.Println("length = ", len(s))
+	fmt.Println("capacity = ", cap(s))
+}
diff --git a/tutorial7-slices/slice_zero_value.go b/tutorial7-slices/slice_zero_value.go
@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	var s []int
+	fmt.Printf("s = %v, len = %d, cap = %d\n", s, len(s), cap(s))
+
+	if s == nil {
+		fmt.Println("s is nil")
+	}
+}
diff --git a/tutorial7-slices/slicing_a_slice.go b/tutorial7-slices/slicing_a_slice.go
@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+func main() {
+	var cities = []string{"New York", "London", "Chicago", "Beijing", "Delhi", "Mumbai", "Bangalore", "Hyderabad", "Hong Kong"}
+
+	var asianCities = cities[3:]
+	var indianCities = asianCities[1:5]
+
+	fmt.Println("cities = ", cities)
+	fmt.Println("asianCities = ", asianCities)
+	fmt.Println("indianCities = ", indianCities)
+}
diff --git a/tutorial8-maps/map_access_key.go b/tutorial8-maps/map_access_key.go
@@ -0,0 +1,18 @@
+package main
+
+import "fmt"
+
+func main() {
+	var employeeSalary = map[string]float64{
+		"John":  78000.00,
+		"Steve": 160000.50,
+		"David": 85000.00,
+	}
+
+	var salary = employeeSalary["Steve"]
+	fmt.Printf("Steve's Salary = %f\n", salary)
+
+	// If a key doesn't exist in the map, we get the zero value of the value type
+	salary = employeeSalary["Jack"]
+	fmt.Printf("Jack's Salary = %f\n", salary)
+}
diff --git a/tutorial8-maps/map_add_keys.go b/tutorial8-maps/map_add_keys.go
@@ -0,0 +1,22 @@
+package main
+
+import "fmt"
+
+func main() {
+	// Initializing a map
+	var tinderMatch = make(map[string]string)
+
+	// Adding keys to a map
+	tinderMatch["Rajeev"] = "Angelina" // Assigns the value "Angelina" to the key "Rajeev"
+	tinderMatch["James"] = "Sophia"
+	tinderMatch["David"] = "Emma"
+
+	fmt.Println(tinderMatch)
+
+	/*
+	  Adding a key that already exists will simply override
+	  the existing key with the new value
+	*/
+	tinderMatch["Rajeev"] = "Jennifer"
+	fmt.Println(tinderMatch)
+}
diff --git a/tutorial8-maps/map_check_key_exists.go b/tutorial8-maps/map_check_key_exists.go
@@ -0,0 +1,31 @@
+package main
+
+import "fmt"
+
+func main() {
+	var employees = map[int]string{
+		1001: "Rajeev",
+		1002: "Sachin",
+		1003: "James",
+	}
+
+	printEmployee(employees, 1001)
+	printEmployee(employees, 1010)
+
+	if isEmployeeExists(employees, 1002) {
+		fmt.Println("EmployeeId 1002 found")
+	}
+}
+
+func printEmployee(employees map[int]string, employeeId int) {
+	if name, ok := employees[employeeId]; ok {
+		fmt.Printf("name = %s, ok = %v\n", name, ok)
+	} else {
+		fmt.Printf("EmployeeId %d not found\n", employeeId)
+	}
+}
+
+func isEmployeeExists(employees map[int]string, employeeId int) bool {
+	_, ok := employees[employeeId]
+	return ok
+}
diff --git a/tutorial8-maps/map_declaration.go b/tutorial8-maps/map_declaration.go
@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+func main() {
+	var m map[string]int
+	fmt.Println(m)
+	if m == nil {
+		fmt.Println("m is nil")
+	}
+
+	// The following statement will result in a runtime error
+	// m["key"] = 100
+}
diff --git a/tutorial8-maps/map_delete_key.go b/tutorial8-maps/map_delete_key.go
@@ -0,0 +1,22 @@
+package main
+
+import "fmt"
+
+func main() {
+	var fileExtensions = map[string]string{
+		"Python": ".py",
+		"C++":    ".cpp",
+		"Java":   ".java",
+		"Golang": ".go",
+		"Kotlin": ".kt",
+	}
+
+	fmt.Println(fileExtensions)
+
+	delete(fileExtensions, "Kotlin")
+
+	// delete function doesn't do anything if the key doesn't exist
+	delete(fileExtensions, "Javascript")
+
+	fmt.Println(fileExtensions)
+}
diff --git a/tutorial8-maps/map_initialize_using_make.go b/tutorial8-maps/map_initialize_using_make.go
@@ -0,0 +1,21 @@
+package main
+
+import "fmt"
+
+func main() {
+	var m = make(map[string]int)
+
+	fmt.Println(m)
+
+	if m == nil {
+		fmt.Println("m is nil")
+	} else {
+		fmt.Println("m is not nil")
+	}
+
+	// make() function returns an initialized and ready to use map.
+	// Since it is initialized, you can add new keys to it.
+	m["one hundred"] = 100
+	fmt.Println(m)
+
+}
diff --git a/tutorial8-maps/map_iterate.go b/tutorial8-maps/map_iterate.go
diff --git a/tutorial8-maps/map_literal.go b/tutorial8-maps/map_literal.go
diff --git a/tutorial8-maps/map_reference_type.go b/tutorial8-maps/map_reference_type.go
