Kuidas implementida tüübi summa (type sum) Go keeles?

In Go, there is no direct support for type sums (type sum), as in some functional languages (Haskell, Scala). However, a similar effect can be achieved using interfaces and type switch.

An interface in Go describes a set of methods, and any type that implements these methods satisfies the interface. To implement type sums, you can define an interface without methods (empty interface interface{}) or with common methods, and then use a type switch to determine the specific type at runtime.

Example:

package main

import "fmt"

type Shape interface{} // empty interface, can be any type

func area(s Shape) float64 {
    switch v := s.(type) {
    case Circle:
        return 3.14 * v.Radius * v.Radius
    case Rectangle:
        return v.Width * v.Height
    default:
        return 0
    }
}

type Circle struct {
    Radius float64
}

type Rectangle struct {
    Width, Height float64
}

func main() {
    c := Circle{Radius: 5}
    r := Rectangle{Width: 3, Height: 4}

    fmt.Println(area(c)) // 78.5
    fmt.Println(area(r)) // 12
}

This way, interfaces and type switch allow implementing behavior similar to a type sum, where a variable can take values of different types, and the corresponding logic is executed depending on the type.