diffdice.go

package main

import (
	"fmt"
	"math/rand"
)

func rollDice() int {
	return rand.Intn(6) + 1
}

type generator func() int
type strategy func(generator) generator

func applyStrategy(g generator, strats ...strategy) generator {
	for _, s := range strats {
		g = s(g)
	}
	return g
}

func reroll(g generator) generator{
	return func() int {
		n := g()
		if n < 5 {
			return g()
		}
		return n
	}
}

func addOne(g generator) generator {
	return func() int {
		n := g()
		if n < 5 {
			return n + 1
		}
		return n
	}
}

func successRate(rolls []int) float64 {
	var oks int
	for _, v := range rolls {
		if v == 5 || v == 6 {
			oks++
		}
	}
	return float64(oks) / float64(len(rolls))
}

func generateRolls(n int, gen func() int) []int {
	var rolls []int
	for i := 0; i < n; i++ {
		rolls = append(rolls, gen())
	}
	return rolls
}

func main() {
	fmt.Println(successRate(generateRolls(1000000, rollDice)))
	fmt.Println(successRate(generateRolls(1000000, applyStrategy(rollDice, reroll))))
	fmt.Println(successRate(generateRolls(1000000, applyStrategy(rollDice, addOne))))
	fmt.Println(successRate(generateRolls(1000000, applyStrategy(rollDice, addOne, reroll))))
	fmt.Println(successRate(generateRolls(1000000, applyStrategy(rollDice, reroll, addOne))))
}