package main

import "fmt"

type point struct {
    x, y float64
}

func (p point) String() string {
    return fmt.Sprintf("(%.1f,%.1f)", p.x, p.y)
}

type triangle struct {
    p1, p2, p3 point
}

func (t *triangle) String() string {
    return fmt.Sprintf("Triangle%s,%s,%s", t.p1, t.p2, t.p3)
}

func (t *triangle) det2D() float64 {
    return t.p1.x * (t.p2.y - t.p3.y) +
           t.p2.x * (t.p3.y - t.p1.y) +
           t.p3.x * (t.p1.y - t.p2.y) 
}

func (t *triangle) checkTriWinding(allowReversed bool) {
    detTri := t.det2D()
    if detTri < 0.0 {
        if allowReversed {
            a := t.p3
            t.p3 = t.p2
            t.p2 = a
        } else {
            panic("Triangle has wrong winding direction.")
        }
    }
}

func boundaryCollideChk(t *triangle, eps float64) bool {
    return t.det2D() < eps
}

func boundaryDoesntCollideChk(t *triangle, eps float64) bool {
    return t.det2D() <= eps
}

func triTri2D(t1, t2 *triangle, eps float64, allowReversed, onBoundary bool) bool {