updates
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// A function can return multiple values.
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package main
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import "fmt"
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func vals() (int, int) { // The `(int, int)` in this signature shows that the
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return 3, 7 // function returns 2 ints.
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}
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func main() {
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x, y := vals() // Use the 2 different return values from the call.
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fmt.Println(x)
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fmt.Println(y)
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}
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/*
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$ go run 21-returns.go
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3
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7
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*/
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23
020-returns/returns.go
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23
020-returns/returns.go
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// ## Multiple Return Values
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// In Go, a function can return multiple values.
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// This feature is used often, for example to
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// return a result and an error from a function.
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package main
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import "fmt"
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// The `(int, int)` in this signature shows that the
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// function returns 2 ints.
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func vals() (int, int) {
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return 3, 7
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}
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func main() {
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// Use the 2 different return values from the call.
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x, y := vals()
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fmt.Println(x)
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fmt.Println(y)
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}
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3
020-returns/returns.sh
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3
020-returns/returns.sh
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$ go run returns.go
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3
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7
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package main // Varadic functions can be called with any number of
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// trailing arguments.
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import "fmt"
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func add(nums ...int) int { // Varadic args are declared with `...type` and
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fmt.Print(nums, " ") // passed in as a slice.
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total := 0
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for _, num := range nums {
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total += num
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}
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return total
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}
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func main() {
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fmt.Println(add(1, 2)) // Varadic functions can be called in the usual way.
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fmt.Println(add(1, 2, 3))
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nums := []int{1, 2, 3, 4} // If you already have multiple args in a slice,
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fmt.Println(add(nums...)) // apply them to a varadic function using `
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} // func(slice...)`.
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/*
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$ go run varadic.go
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[1 2] 3
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[1 2 3] 6
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[1 2 3 4] 10
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*/
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33
021-varadic/varadic.go
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33
021-varadic/varadic.go
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// ## Varadic Functions
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// Varadic functions can be called with any number of
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// trailing arguments. This is useful if you don't know
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// number of arguments that will be needed for a function
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// ahead of time.
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package main
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import "fmt"
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// Varadic args are declared with `...type` and
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// passed in as a slice.
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func add(nums ...int) int {
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fmt.Print(nums, " ")
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total := 0
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for _, num := range nums {
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total += num
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}
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return total
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}
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func main() {
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// Varadic functions can be called in the usual way.
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fmt.Println(add(1, 2))
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fmt.Println(add(1, 2, 3))
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// If you already have multiple args in a slice,
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// apply them to a varadic function using `
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// func(slice...)`.
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nums := []int{1, 2, 3, 4}
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fmt.Println(add(nums...))
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}
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4
021-varadic/varadic.sh
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4
021-varadic/varadic.sh
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$ go run varadic.go
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[1 2] 3
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[1 2 3] 6
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[1 2 3 4] 10
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// ## Closures
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package main
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package main
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import "fmt"
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import "fmt"
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// ## Recursion
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package main
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package main
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import "fmt"
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import "fmt"
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// ## Defer
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package main
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package main
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import "fmt"
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import "fmt"
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// Panic
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// A `panic` means something went unexpectedly wrong.
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// Mostly we use it to fail fast on errors that
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// shouldn't occur during normal operation.
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package main
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func main() {
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panic("O noes") // We'll use panic throught this book to check for
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} // unexpected errors. This is the only program in the
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// book designed to panic.
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/*
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$ go run 26-panic.go
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panic: O noes
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goroutine 1 [running]:
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main.main()
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/.../src/26-panic.go:4 +0x47
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...
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*/
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13
025-panic/panic.go
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13
025-panic/panic.go
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// ## Panic
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// A `panic` means something went unexpectedly wrong.
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// Mostly we use it to fail fast on errors that
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// shouldn't occur during normal operation.
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package main
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func main() {
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// We'll use panic throught this book to check for
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// unexpected errors. This is the only program in the
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// book designed to panic.
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panic("O noes")
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}
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7
025-panic/panic.sh
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7
025-panic/panic.sh
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$ go run 26-panic.go
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panic: O noes
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goroutine 1 [running]:
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main.main()
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/.../src/26-panic.go:4 +0x47
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...
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// ## Recover
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package main
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package main
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import "fmt"
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import "fmt"
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// ## Pointers
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package main
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package main
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import "fmt"
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import "fmt"
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