2016 Update

Task/Ray-casting-algorithm/Go/ray-casting-algorithm-1.go

@@ -1,8 +1,8 @@
 package main
 
 import (
-    "math"
     "fmt"
+    "math"
 )
 
 type xy struct {
@@ -85,7 +85,12 @@ var tpg = []poly{
         {p13, p14}, {p14, p9}, {p9, p11}}},
 }
 
-var tpt = []xy{{5, 5}, {5, 8}, {-10, 5}, {0, 5}, {10, 5}, {8, 5}, {10, 10}}
+var tpt = []xy{
+    // test points common in other solutions on this page
+    {5, 5}, {5, 8}, {-10, 5}, {0, 5}, {10, 5}, {8, 5}, {10, 10},
+    // test points that show the problem with "strange"
+    {1, 2}, {2, 1},
+}
 
 func main() {
     for _, pg := range tpg {

Task/Ray-casting-algorithm/Go/ray-casting-algorithm-3.go

@@ -0,0 +1,50 @@
+package main
+
+import "fmt"
+
+type xy struct {
+    x, y float64
+}
+
+type closedPoly struct {
+    name string
+    vert []xy
+}
+
+func inside(pt xy, pg closedPoly) bool {
+    if len(pg.vert) < 3 {
+        return false
+    }
+    in := rayIntersectsSegment(pt, pg.vert[len(pg.vert)-1], pg.vert[0])
+    for i := 1; i < len(pg.vert); i++ {
+        if rayIntersectsSegment(pt, pg.vert[i-1], pg.vert[i]) {
+            in = !in
+        }
+    }
+    return in
+}
+
+func rayIntersectsSegment(p, a, b xy) bool {
+    return (a.y > p.y) != (b.y > p.y) &&
+        p.x < (b.x-a.x)*(p.y-a.y)/(b.y-a.y)+a.x
+}
+
+var tpg = []closedPoly{
+    {"square", []xy{{0, 0}, {10, 0}, {10, 10}, {0, 10}}},
+    {"square hole", []xy{{0, 0}, {10, 0}, {10, 10}, {0, 10}, {0, 0},
+        {2.5, 2.5}, {7.5, 2.5}, {7.5, 7.5}, {2.5, 7.5}, {2.5, 2.5}}},
+    {"strange", []xy{{0, 0}, {2.5, 2.5}, {0, 10}, {2.5, 7.5}, {7.5, 7.5},
+        {10, 10}, {10, 0}, {2.5, 2.5}}},
+    {"exagon", []xy{{3, 0}, {7, 0}, {10, 5}, {7, 10}, {3, 10}, {0, 5}}},
+}
+
+var tpt = []xy{{1, 2}, {2, 1}}
+
+func main() {
+    for _, pg := range tpg {
+        fmt.Printf("%s:\n", pg.name)
+        for _, pt := range tpt {
+            fmt.Println(pt, inside(pt, pg))
+        }
+    }
+}