vector.go

// vector.go
package main

import (
	"fmt"
	"math"
)

type Vector struct {
	x, y, z float64
}

// v.Dot(u) -> float64
func (v Vector) Dot(u Vector) float64 {
	return (v.x*u.x + v.y*u.y + v.z*u.z)
}

func (v Vector) Cross(u Vector) (r Vector) {
	r.x = u.y*v.z - u.z*v.y
	r.y = u.z*v.z - u.x*v.z
	r.z = u.x*v.y - u.y*v.x
	return
}

func (v Vector) Module() float64 {
	return math.Sqrt(v.x*v.x + v.y*v.y + v.z*v.z)
}

func (v Vector) Normalize() Vector {
	if m := v.Module(); m != 0.0 {
		return Vector{v.x / m, v.y / m, v.z / m}
	}
	return v
}

func (v Vector) Add(u Vector) Vector {
	return Vector{v.x + u.x, v.y + u.y, v.z + u.z}
}

func (v Vector) Sub(u Vector) Vector {
	return Vector{v.x - u.x, v.y - u.y, v.z - u.z}
}

func (v Vector) Mul(u float64) Vector {
	return Vector{v.x * u, v.y * u, v.z * u}
}

func (v Vector) String() string {
	return fmt.Sprintf("<Vec: %.2f %.2f %.2f>", v.x, v.y, v.z)
}