cs_joke.go

package main

import (
	"fmt"
	"strconv"
	"strings"
)

type ProblemCounter int

type HardProblems int

const (
	naming HardProblems = 1 << iota
	counting
)

func main() {
	const hardProblems = naming | counting
	fmt.Printf("There are %s hard problems in computer science: %s.", ProblemCounter(hardProblems), hardProblems)
}

func (n ProblemCounter) String() string {
	if n == 3 {
		return "three"
	}
	return strconv.Itoa(int(n))
}

func (hp HardProblems) String() string {
	res := make([]string, 0, 2)
	if hp&naming != 0 {
		res = append(res, "naming things")
	}

	if hp&counting != 0 {
		res = append(res, "counting things")
	}

	if len(res) > 0 {
		return strings.Join(res, " and ")
	}
	return "UNKNOWN"
}

Live code - https://play.golang.org/p/bgrThQvJBH
Output:

There are three hard problems in computer science: naming things and counting things.