package go_36
import ( "errors" "fmt" "testing")
type Printer func(contents string) (n int, err error)
func printToStd(contents string) (bytesNum int, err error) { return fmt.Println(contents)}
func TestDemo26(t *testing.T) { var p Printer p = printToStd a, e := p("something123") fmt.Println(a, e)}
type operate func(x, y int) int
// 方案 1func calculate(x int, y int, op operate) (int, error) { if op == nil { return 0, errors.New("invalid operation") } return op(x, y), nil}
// 方案 2type calculateFunc func(x int, y int) (int, error)
func genCalculator(op operate) calculateFunc { return func(x int, y int) (int, error) { if op == nil { return 0, errors.New("invalid operation") } return op(x, y), nil }}
func TestDemo27(t *testing.T) { // 方案 1 x, y := 12, 23 op := func(x, y int) int{ return x * y } result, err := calculate(x, y, op) fmt.Println(result, err) result, err = calculate(x, y, nil) fmt.Println(result, err)
// 方案 2 x, y = 56, 78 add := genCalculator(op) result, err = add(x, y) fmt.Println(result, err)}
func modifyArray(a [3]string) [3]string { a[1] = "x" return a}
func modifySlice(a []string) []string { a[1] = "slice" return a}
func modifyComplexArray(a [3][]string) [3][]string { a[1][1] = "slice" a[2] = []string{"new", "array", "q"} return a}
func TestDemo28(t *testing.T) { // 示例 1，修改数组，原始数组不变 array1 := [3]string{"a", "b", "c"} fmt.Println(array1) array2 := modifyArray(array1) fmt.Println(array2) fmt.Println(array1)
// 示例 2，修改切片，原始切片变化 slice1 := []string{"x", "y", "z"} fmt.Println(slice1) slice2 := modifySlice(slice1) fmt.Println(slice2) fmt.Println(slice1)
// 示例 3，修改数组时，原始数组不变；修改数组中切片，原始切片变化 complexArray1 := [3][]string { []string{"d", "e", "f"}, []string{"g", "h", "i"}, []string{"j", "k", "l"}, } fmt.Println(complexArray1) complexArray2 := modifyComplexArray(complexArray1) fmt.Println(complexArray2) fmt.Println(complexArray1)}
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