The subtle relationship between Golang function addresses and pointers

The function address points to the memory address of the function itself, while the pointer points to the memory address of the variable or structure. However, function addresses can also be stored in pointers, allowing us to call functions through pointers. These concepts are useful in various scenarios, such as dynamically calling functions or creating callback functions.

Function address and pointer in Go: subtle relationship

In Go language, function address and pointer seem to be similar, But there are subtle differences between them. Understanding their differences is critical to writing efficient and maintainable code.

Function address

The function address is the address pointing to the memory location of the function itself. It can be obtained through the compiler-generated func literal or the ValueOf or Func function in the reflect package.

Pointer

A pointer is a variable that stores the address of another value. In Go, pointers can be declared via * symbols and type names. For example, *int is a pointer to an integer value.

The relationship between them

Function addresses and pointers point to different things. A function address points to the memory address of the function itself, while a pointer points to the memory address of a variable or structure. However, function addresses can also be stored in pointers.

In the following example:

func myFunc() {}
var fptr = &myFunc

fptr is a pointer pointing to the address of function myFunc. This allows us to call functions through pointers:

(*fptr)() // 等同于 myFunc()

Practical Example

Function addresses and pointers are useful in various scenarios. Here is a practical example that utilizes these concepts:

package main

import (
    "fmt"
    "math"
)

// 计算半径的函数
func radius(n int) float64 {
    return float64(n) / 2.0
}

// 求一个数字的根的函数
func sqrt(n int) float64 {
    return math.Sqrt(float64(n))
}

var operations = map[string]func(int) float64{
    "radius": radius,
    "sqrt":    sqrt,
}

func main() {
    input := "sqrt"
    num := 9

    // 通过名称获取函数指针
    op := operations[input]

    // 调用函数并打印结果
    fmt.Println(op(num))
}

This example demonstrates how to store function addresses in a dictionary and dynamically call them by function name at runtime.

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