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pt-br/code/src/apps/ch.2.3/basic_functions/main.go

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+// Example code for Chapter 2.3 from "Build Web Application with Golang"
+// Purpose: Creating a basic function
+package main
+
+import "fmt"
+
+// return greater value between a and b
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+func main() {
+	x := 3
+	y := 4
+	z := 5
+
+	max_xy := max(x, y) // call function max(x, y)
+	max_xz := max(x, z) // call function max(x, z)
+
+	fmt.Printf("max(%d, %d) = %d\n", x, y, max_xy)
+	fmt.Printf("max(%d, %d) = %d\n", x, z, max_xz)
+	fmt.Printf("max(%d, %d) = %d\n", y, z, max(y, z)) // call function here
+}

pt-br/code/src/apps/ch.2.3/hidden_print_methods/main.go

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+// As of Google go 1.1.2, `println()` and `print()` are hidden functions included from the runtime package.
+// However it's encouraged to use the print functions from the `fmt` package.
+package main
+
+import "fmt"
+
+func f() {
+	fmt.Println("First")
+	print("Second ")
+	println(" Third")
+}
+func main() {
+	f()
+}

pt-br/code/src/apps/ch.2.3/import_packages/main.go

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+// Example code for Chapter 2.3 from "Build Web Application with Golang"
+// Purpose: Shows different ways of importing a package.
+// Note: For the package `only_call_init`, we reference the path from the
+// base directory of `$GOPATH/src`. The reason being Golang discourage
+// the use of relative paths when import packages.
+// BAD: "./only_call_init"
+// GOOD: "apps/ch.2.3/import_packages/only_call_init"
+package main
+
+import (
+	// `_` will only call init() inside the package only_call_init
+	_ "apps/ch.2.3/import_packages/only_call_init"
+	f "fmt"         // import the package as `f`
+	. "math"        // makes the public methods and constants global
+	"mymath"        // custom package located at $GOPATH/src/
+	"os"            // normal import of a standard package
+	"text/template" // the package takes the name of last folder path, `template`
+)
+
+func main() {
+	f.Println("mymath.Sqrt(4) =", mymath.Sqrt(4))
+	f.Println("E =", E) // references math.E
+
+	t, _ := template.New("test").Parse("Pi^2 = {{.}}")
+	t.Execute(os.Stdout, Pow(Pi, 2))
+}

pt-br/code/src/apps/ch.2.3/import_packages/only_call_init/only_call_init.go

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+package only_call_init
+
+import "fmt"
+
+func init() {
+	fmt.Println("only_call_init.init() was called.")
+}

pt-br/code/src/apps/ch.2.3/main.go

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+// Example code for Chapter 2.3 from "Build Web Application with Golang"
+// Purpose: Goes over if, else, switch conditions, loops and defer.
+package main
+
+import "fmt"
+
+func computedValue() int {
+	return 1
+}
+func show_if() {
+	fmt.Println("\n#show_if()")
+	x := computedValue()
+	integer := 23
+
+	fmt.Println("x =", x)
+	fmt.Println("integer =", integer)
+	if x > 10 {
+		fmt.Println("x is greater than 10")
+	} else {
+		fmt.Println("x is less than 10")
+	}
+
+	if integer == 3 {
+		fmt.Println("The integer is equal to 3")
+	} else if integer < 3 {
+		fmt.Println("The integer is less than 3")
+	} else {
+		fmt.Println("The integer is greater than 3")
+	}
+}
+func show_if_var() {
+	fmt.Println("\n#show_if_var()")
+	// initialize x, then check if x greater than
+	if x := computedValue(); x > 10 {
+		fmt.Println("x is greater than 10")
+	} else {
+		fmt.Println("x is less than 10")
+	}
+
+	// the following code will not compile, since `x` is only accessable with the if/else block
+	// fmt.Println(x)
+}
+func show_goto() {
+	fmt.Println("\n#show_goto()")
+	// The call to the label switches the goroutine it seems.
+	i := 0
+Here: // label ends with ":"
+	fmt.Println(i)
+	i++
+	if i < 10 {
+		goto Here // jump to label "Here"
+	}
+}
+func show_for_loop() {
+	fmt.Println("\n#show_for_loop()")
+	sum := 0
+	for index := 0; index < 10; index++ {
+		sum += index
+	}
+	fmt.Println("part 1, sum is equal to ", sum)
+
+	sum = 1
+	// The compiler will remove the `;` from the line below.
+	// for ; sum < 1000 ; {
+	for sum < 1000 {
+		sum += sum
+	}
+	fmt.Println("part 2, sum is equal to ", sum)
+
+	for index := 10; 0 < index; index-- {
+		if index == 5 {
+			break // or continue
+		}
+		fmt.Println(index)
+	}
+
+}
+func show_loop_through_map() {
+	fmt.Println("\n#show_loop_through_map()")
+	m := map[string]int{
+		"one":   1,
+		"two":   2,
+		"three": 3,
+	}
+	fmt.Println("map value = ", m)
+	for k, v := range m {
+		fmt.Println("map's key: ", k)
+		fmt.Println("map's value: ", v)
+	}
+}
+func show_switch() {
+	fmt.Println("\n#show_switch()")
+	i := 10
+	switch i {
+	case 1:
+		fmt.Println("i is equal to 1")
+	case 2, 3, 4:
+		fmt.Println("i is equal to 2, 3 or 4")
+	case 10:
+		fmt.Println("i is equal to 10")
+	default:
+		fmt.Println("All I know is that i is an integer")
+	}
+
+	integer := 6
+	fmt.Println("integer =", integer)
+	switch integer {
+	case 4:
+		fmt.Println("integer == 4")
+		fallthrough
+	case 5:
+		fmt.Println("integer <= 5")
+		fallthrough
+	case 6:
+		fmt.Println("integer <= 6")
+		fallthrough
+	case 7:
+		fmt.Println("integer <= 7")
+		fallthrough
+	case 8:
+		fmt.Println("integer <= 8")
+		fallthrough
+	default:
+		fmt.Println("default case")
+	}
+}
+func show_defer() {
+	fmt.Println("\nshow_defer()")
+	defer fmt.Println("(last defer)")
+	for i := 0; i < 5; i++ {
+		defer fmt.Printf("%d ", i)
+	}
+}
+func main() {
+	show_if()
+	show_if_var()
+	show_goto()
+	show_for_loop()
+	show_loop_through_map()
+	show_switch()
+	show_defer()
+}

pt-br/code/src/apps/ch.2.3/panic_and_recover/main.go

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+// Example code for Chapter 2.3 from "Build Web Application with Golang"
+// Purpose: Showing how to use `panic()` and `recover()`
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+var user = os.Getenv("USER")
+
+func check_user() {
+	if user == "" {
+		panic("no value for $USER")
+	}
+	fmt.Println("Environment Variable `USER` =", user)
+}
+func throwsPanic(f func()) (b bool) {
+	defer func() {
+		if x := recover(); x != nil {
+			fmt.Println("Panic message =", x);
+			b = true
+		}
+	}()
+	f() // if f causes panic, it will recover
+	return
+}
+func main(){
+	didPanic := throwsPanic(check_user)
+	fmt.Println("didPanic =", didPanic)
+}

pt-br/code/src/apps/ch.2.3/pass_by_value_and_pointer/main.go

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+// Example code for Chapter 2.3 from "Build Web Application with Golang"
+// Purpose: Shows passing a variable by value and reference
+package main
+
+import "fmt"
+
+func add_by_value(a int) int {
+	a = a + 1
+	return a 
+}
+func add_by_reference(a *int) int {
+	*a = *a + 1 
+	return *a  
+}
+func show_add_by_value() {
+	x := 3
+	fmt.Println("x = ", x)
+	fmt.Println("add_by_value(x) =", add_by_value(x) )
+	fmt.Println("x = ", x)
+}
+func show_add_by_reference() {
+	x := 3
+	fmt.Println("x = ", x) 
+	// &x pass memory address of x
+	fmt.Println("add_by_reference(&x) =", add_by_reference(&x) )
+	fmt.Println("x = ", x) 
+}
+func main() {
+	show_add_by_value()
+	show_add_by_reference()
+}

pt-br/code/src/apps/ch.2.3/type_function/main.go

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+// Example code for Chapter 2.3 from "Build Web Application with Golang"
+// Purpose: Shows how to define a function type
+package main
+
+import "fmt"
+
+type testInt func(int) bool // define a function type of variable
+
+func isOdd(integer int) bool {
+	if integer%2 == 0 {
+		return false
+	}
+	return true
+}
+
+func isEven(integer int) bool {
+	if integer%2 == 0 {
+		return true
+	}
+	return false
+}
+
+// pass the function `f` as an argument to another function
+
+func filter(slice []int, f testInt) []int {
+	var result []int
+	for _, value := range slice {
+		if f(value) {
+			result = append(result, value)
+		}
+	}
+	return result
+}
+func init() {
+	fmt.Println("\n#init() was called.")
+}
+func main() {
+	slice := []int{1, 2, 3, 4, 5, 7}
+	fmt.Println("slice = ", slice)
+	odd := filter(slice, isOdd) // use function as values
+	fmt.Println("Odd elements of slice are: ", odd)
+	even := filter(slice, isEven)
+	fmt.Println("Even elements of slice are: ", even)
+}

pt-br/code/src/apps/ch.2.3/variadic_functions/main.go

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+// Example code for Chapter 2.3 from "Build Web Application with Golang"
+// Purpose: Shows how to return multiple values from a function
+package main
+
+import "fmt"
+
+// return results of A + B and A * B
+func SumAndProduct(A, B int) (int, int) {
+	return A + B, A * B
+}
+
+func main() {
+	x := 3
+	y := 4
+
+	xPLUSy, xTIMESy := SumAndProduct(x, y)
+
+	fmt.Printf("%d + %d = %d\n", x, y, xPLUSy)
+	fmt.Printf("%d * %d = %d\n", x, y, xTIMESy)
+}