golang function nested function parameter passing

Go functions can be nested, and embedded functions can access external function variables. Parameter passing methods include: passing by value (copying the value) and passing by reference (passing the address). Nested functions and parameter passing are used in practical applications, such as calculating the average of an array and modifying external variables by passing by reference to achieve flexible data processing.

Go function nested function parameter passing

Functions in Go can be nested, which means that a function can be defined in inside another function. Nested functions can access variables of outer functions, but not vice versa.

Syntax

The syntax of nested functions is as follows:

func outerFunction(args ...) {
  func innerFunction(args ...) {
    // 访问外部函数的变量
  }
}

Parameter passing

When nested When a function is called, its arguments can be passed to external functions. Parameters can be passed in the following ways:

• Pass by value: Parameter values ​​are copied and passed to the nested function.
• Pass by reference: The address of the parameter is passed to the nested function.

Example of passing by value:

func outerFunction(x int) {
  func innerFunction(y int) {
    fmt.Println(x + y) // 输出 x + y
  }

  innerFunction(10)
}

func main() {
  outerFunction(5) // 输出 15
}

Example of passing by reference:

func outerFunction(x *int) {
  func innerFunction(y *int) {
    *y += *x // 更改外部函数的变量 x
  }

  innerFunction(x)
}

func main() {
  x := 5
  outerFunction(&x)
  fmt.Println(x) // 输出 10
}

Practical case

The following is a practical case using nested functions and passing by reference:

func calculateAverage(data []int) {
  sum := 0

  // 内嵌函数用于计算数组中的每个元素的总和
  func sumArray(data []int) {
    for _, v := range data {
      sum += v
    }
  }

  sumArray(data)
  return float64(sum) / float64(len(data))
}

func main() {
  data := []int{1, 2, 3, 4, 5}
  fmt.Println(calculateAverage(data)) // 输出 3.0
}

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