decimal.go

package main

import (
	"fmt"
)

type usd int64

func USD(f float64) usd {
	return usd((f * 100) + 0.5)
}

func (m usd) float() float64 {
	x := float64(m)
	x = x / 100
	return x
}

func (m usd) multiply(f float64) usd {
	x := (float64(m) * f) + 0.5
	return usd(x)
}

func (m usd) String() string {
	x := float64(m)
	x = x / 100
	return fmt.Sprintf("$%.2f", x)
}

func main() {
	fmt.Println("Product costs $9.09. Tax is 9.75%.")

	f := 9.09
    	t := 0.0975
    	ft := f * t
    	fmt.Printf("Floats: %.18f * %.18f = %.18f\n", f, t, ft)
	
	u := USD(9.09)
	ut := u.multiply(t)
	fmt.Printf("USD:    %v * %v = %v\n", u, t, ut)
}