Golang：确定功能的泛函？

Question

Is it possible to write a function to determine the arity of arbitrary functions, such that:

1.

func mult_by_2(x int) int {
      return 2 * x
}
fmt.Println(arity(mult_by_2)) //Prints 1

2.

func add(x int, y int) int {
      return x + y
}
fmt.Println(arity(add)) //Prints 2

3.

func add_3_ints(a, b, c int) int {
      return b + a + c
}
fmt.Println(arity(add_3_ints)) //Prints 3

Answer 1

You can write such a function using the reflect package:

import (
    "reflect"
)

func arity(value interface{}) int {
    ref := reflect.ValueOf(value)
    tpye := ref.Type()
    if tpye.Kind() != reflect.Func {
        // You could define your own logic here
        panic("value is not a function")
    }
    return tpye.NumIn()
}