railway.go

package main

import "fmt"

func alfa(i int) (int, error) {
	if i > 1 {
		return i, nil
	}

	return 0, fmt.Errorf("i was greater than 1")
}

func beta(i int) (int, error) {
	if i % 2 == 0 {
		return i, nil
	}

	return 0, fmt.Errorf("i was odd")
}

func gamma(i int) (int, error) {
	if i < 100 {
		return i, nil
	}

	return 0, fmt.Errorf("i was less than 100")
}

func doWithoutError(i int, err error, f func(int) (int, error)) (int, error) {
	if err != nil {
		return i, err
	}

	return f(i)
}

func regular(i int) int {
	i, err := alfa(i)
	if err != nil {
		panic(err)
	}

	i, err = beta(i)
	if err != nil {
		panic(err)
	}

	i, err = gamma(i)
	if err != nil {
		panic(err)
	}

	return i
}

func railway(i int) int {
	i, err := alfa(i)
	i, err = doWithoutError(i, err, beta)
	i, err = doWithoutError(i, err, gamma)

	if err != nil {
		panic(err)
	}

	return i
}

// https://www.journal.petrausch.info/post/2020/05/must-pattern/
func main() {
	input := 2
	fmt.Println(regular(input))
	fmt.Println(railway(input))
}