// Function to calculate the Beers, 1964 tree volume
// from diameter at breast height and merchantable height
// by David R. Larsen, October 11, 2012
// Creative Commons,  http://creativecommons.org/licenses/by-nc/3.0/us/
package main

import (
	"fmt"
	"math"
)

func treeVolume(dbh float64, mht float64, volumeType string) float64 {
	var volume float64
	if mht > 0.0 {
		a := (math.Pow(dbh, 2.0) * (dbh + 190.0)) / 100000.0
		b := 1.0 / 100.0 * ((mht*(168.0-mht))/64.0 + (32.0 / mht))
		c := 475.0 + (3.0*math.Pow(mht, 2.0))/128.0

		if volumeType == "cords" {
			volume = a * b
		} else if volumeType == "cubic" {
			volume = 76.0 * a * b
		} else if volumeType == "cubicbark" {
			volume = 92.0 * a * b
		} else if volumeType == "boardfeet" {
			volume = a * b * c
		} else {
			volume = 0.0
		}
		return volume
	}
	return 0.0
}

func main() {
	fmt.Println("Cords =", treeVolume(10, 26, "cords"))
	fmt.Println("Cubic =", treeVolume(10, 26, "cubic"))
	fmt.Println("Cubic with bark =", treeVolume(10, 26, "cubicbark"))
	fmt.Println("International 1/4 boardfeet =", treeVolume(10, 26, "boardfeet"))
}