tasks a-s

Task/Ray-casting-algorithm/Ada/ray-casting-algorithm-2.ada

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+package body Polygons is
+   EPSILON : constant := 0.00001;
+
+   function Ray_Intersects_Segment
+     (Who   : Point;
+      Where : Segment)
+      return  Boolean
+   is
+      The_Point        : Point   := Who;
+      Above            : Point;
+      Below            : Point;
+      M_Red            : Float;
+      Red_Is_Infinity  : Boolean := False;
+      M_Blue           : Float;
+      Blue_Is_Infinity : Boolean := False;
+   begin
+      if Where (1).Y < Where (2).Y then
+         Above := Where (2);
+         Below := Where (1);
+      else
+         Above := Where (1);
+         Below := Where (2);
+      end if;
+      if The_Point.Y = Above.Y or The_Point.Y = Below.Y then
+         The_Point.Y := The_Point.Y + EPSILON;
+      end if;
+      if The_Point.Y < Below.Y or The_Point.Y > Above.Y then
+         return False;
+      elsif The_Point.X > Above.X and The_Point.X > Below.X then
+         return False;
+      elsif The_Point.X < Above.X and The_Point.X < Below.X then
+         return True;
+      else
+         if Above.X /= Below.X then
+            M_Red := (Above.Y - Below.Y) / (Above.X - Below.X);
+         else
+            Red_Is_Infinity := True;
+         end if;
+         if Below.X /= The_Point.X then
+            M_Blue := (The_Point.Y - Below.Y) / (The_Point.X - Below.X);
+         else
+            Blue_Is_Infinity := True;
+         end if;
+         if Blue_Is_Infinity then
+            return True;
+         elsif Red_Is_Infinity then
+            return False;
+         elsif M_Blue >= M_Red then
+            return True;
+         else
+            return False;
+         end if;
+      end if;
+   end Ray_Intersects_Segment;
+
+   function Create_Polygon (List : Point_List) return Polygon is
+      Result : Polygon (List'Range);
+      Side   : Segment;
+   begin
+      for I in List'Range loop
+         Side (1) := List (I);
+         if I = List'Last then
+            Side (2) := List (List'First);
+         else
+            Side (2) := List (I + 1);
+         end if;
+         Result (I) := Side;
+      end loop;
+      return Result;
+   end Create_Polygon;
+
+   function Is_Inside (Who : Point; Where : Polygon) return Boolean is
+      Count : Natural := 0;
+   begin
+      for Side in Where'Range loop
+         if Ray_Intersects_Segment (Who, Where (Side)) then
+            Count := Count + 1;
+         end if;
+      end loop;
+      if Count mod 2 = 0 then
+         return False;
+      else
+         return True;
+      end if;
+   end Is_Inside;
+
+end Polygons;