Refactor "best" state

geom/alg_rotated_mbr.go

@@ -47,14 +47,15 @@ func RotatedMinimumBoundingRectangle(g Geometry) Geometry {
 	}
 
 	advance := func(idx *int, dist func() float64) {
+		d0 := dist()
 		for {
-			d0 := dist()
 			*idx = (*idx + 1) % seq.Length()
 			d1 := dist()
 			if d1 < d0 {
-				*idx = (*idx + seq.Length() - 1) % seq.Length()
+				*idx = (*idx - 1) % seq.Length()
 				break
 			}
+			d0 = d1
 		}
 	}
 
@@ -66,41 +67,52 @@ func RotatedMinimumBoundingRectangle(g Geometry) Geometry {
 	lhsIdx = farIdx
 	advance(&lhsIdx, lhsDist)
 
-	bestBaseLine := getLine()
-	bestRHSDist := rhsDist()
-	bestFarDist := farDist()
-	bestLHSDist := lhsDist()
-	bestArea := bestFarDist * (bestRHSDist + bestLHSDist)
+	best := struct {
+		base int
+		rhs  int
+		far  int
+		lhs  int
+		area float64
+	}{
+		lnIdx, rhsIdx, farIdx, lhsIdx,
+		farDist() * (rhsDist() + lhsDist()),
+	}
 
 	for {
 		lnIdx++
 		if lnIdx+1 == seq.Length() {
 			break
 		}
-		ln := getLine()
 
 		// Advance calipers:
 		advance(&rhsIdx, rhsDist)
 		advance(&farIdx, farDist)
 		advance(&lhsIdx, lhsDist)
 		area := farDist() * (rhsDist() + lhsDist())
 
-		if area < bestArea {
-			bestBaseLine = ln
-			bestArea = area
-			bestRHSDist = rhsDist()
-			bestFarDist = farDist()
-			bestLHSDist = lhsDist()
+		if area < best.area {
+			best.base = lnIdx
+			best.area = area
+			best.rhs = rhsIdx
+			best.far = farIdx
+			best.lhs = lhsIdx
 		}
 	}
 
-	rhsBasis := bestBaseLine.b.Sub(bestBaseLine.a).Unit()
+	lnIdx = best.base
+	rhsIdx = best.rhs
+	farIdx = best.far
+	lhsIdx = best.lhs
+
+	baseLine := getLine()
+
+	rhsBasis := baseLine.b.Sub(baseLine.a).Unit()
 	farBasis := rhsBasis.rotateCCW90()
 
-	farVec := farBasis.Scale(bestFarDist)
-	rhsVec := rhsBasis.Scale(bestRHSDist)
-	lhsVec := rhsBasis.Scale(-bestLHSDist)
-	origin := bestBaseLine.a
+	rhsVec := rhsBasis.Scale(rhsDist())
+	farVec := farBasis.Scale(farDist())
+	lhsVec := rhsBasis.Scale(-lhsDist())
+	origin := baseLine.a
 
 	pt0 := origin.Add(lhsVec)
 	pt1 := origin.Add(rhsVec)