map by foldl on go

map.go

package main

import (
	"./money"
	"fmt"
)

func main() {
	mon := make([]money.Money, 0, 10)

	mon = append(mon, money.NewSen())
	mon = append(mon, money.NewGosen())
	mon = append(mon, money.NewSen())
	mon = append(mon, money.NewSen())
	mon = append(mon, money.NewSen())
	mon = append(mon, money.NewSen())

	sum := foldl(mon, money.NewZero(), func(m1 money.Money, m2 money.Money) money.Money {
		result := m1.Add(m2)
		return result
	})

	mapped := Map(mon, func(m1 money.Money) money.Money {
		return m1.Add(money.NewSen())
	})

	fmt.Println("sum: ", sum.Price())

	for _, val := range mapped {
		fmt.Println(val)
	}
}

func foldl(ls []money.Money, z money.Money, op func(money.Money, money.Money) money.Money) money.Money {
	if len(ls) == 0 {
		return z
	} else {
		return foldl(ls[1:], op(z, ls[0]), op)
	}
}

func Fold(ls []money.Money, z []money.Money, op func(money.Money, []money.Money) []money.Money) []money.Money {
	if len(ls) == 0 {
		return z
	} else {
		return Fold(ls[1:], op(ls[0], z), op)
	}
}

func Map(ls []money.Money, op func(money.Money) money.Money) []money.Money {
	return Fold(ls, nil, func(v money.Money, l []money.Money) []money.Money {
		return append(l, op(v))
	})
}