What are indefinite parameters in go language?

Indefinite parameters means that the number of parameters passed in by the function is an indefinite number; the indefinite parameter declaration uses the syntax format of "param...type". Characteristics of indefinite parameters: 1. All indefinite parameter types must be the same; 2. The indefinite parameter must be the last parameter of the function; 3. The indefinite parameter is equivalent to a slice in the function body, and the operation of the slice is also suitable for the indefinite parameter operation; 4. Slices can be passed as parameters to indefinite parameters, and "..." must be added after the slice name; 5. The types of functions whose formal parameters are indefinite parameters are different from those of functions whose formal parameters are slices.

The operating environment of this tutorial: Windows 7 system, GO version 1.18, Dell G3 computer.

What are indefinite parameters

Indefinite parameters mean that the number of parameters passed in by the function is an indefinite number.

package main

import (
    "fmt"
)

/*
不定参数函数
*/
func Add(a int, args ...int) (result int) {
    result += a
    for _, arg := range args {
        result += arg
    }
    return
}

func main() {
    fmt.Println(Add(1, 2, 3, 4, 5, 6, 7, 8, 9, 10))
}

The Go function supports an indefinite number of formal parameters. The indefinite parameter declaration uses the syntax format of param...type

The indefinite parameters have the following characteristics:

• ①All variable parameter types must be the same.

• ②The indefinite parameter must be the last parameter of the function.

• ③The indefinite parameter is equivalent to a slice in the function body, and the operation of the slice is also suitable for the operation of the indefinite parameter.

• ④ Slices can also be passed as parameters to indefinite parameters, and "..." must be added after the slice name.

package main

import "fmt"

func Add(arr ...int) int {
	var count int
	arr1 := arr[1:]
	for _, val := range arr1 {
		count += val
	}
	return count
}

func main() {
	slice := []int{1, 2, 3, 4, 5}
	//array := [...]int{1, 2, 3, 4}
	fmt.Println(Add(slice...))
	//fmt.Println(Add(array...))  //cannot use array (variable of type [4]int) as parameter of type []int
}

• ⑤The types of functions whose formal parameters are indefinite parameters are different from those of functions whose formal parameters are slices.

package main

import "fmt"

func Add1(arr ...int) int {
	return arr[0]
}

func Add2(arr []int) int {
	return arr[0]
}

func main() {
	fmt.Printf("%T\n", Add1)
	fmt.Printf("%T\n", Add2)
}

Passing of indefinite parameters

func SetData(args ...int) (result int) {
    //不定参数的传递
    return Add(1, args...)
}
func main() {
    fmt.Println(SetData(1, 2, 3))//输出7
    array := []int{1, 2, 3, 4}
    fmt.Println(Add(1, array...))//输出11
}

Any type of indefinite parameters

/*
任意类型的不定参数，用interface{}表示
*/

func MyPrintf(args ...interface{}) {
    for _, arg := range args { //迭代不定参数
        switch arg.(type) {
        case int:
            fmt.Println(arg, "is int")
        case string:
            fmt.Println(arg, "is string")
        case float64:
            fmt.Println(arg, "is float64")
        case bool:
            fmt.Println(arg, " is bool")
        default:
            fmt.Println("未知的类型")
        }
    }
}

func main() {
    /*输出结果：
                12 is int
                haha is string
                12.5 is float64
                false  is bool
                -12.5 is float64
    */
    MyPrintf(12, "haha", 12.5, false, -12.5)
}

[Related recommendations: Go video tutorial, Programming teaching】

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