Added Difference boolean operation

OSCADSharp/OSCADSharp.ConsoleTests/Program.cs

@@ -31,7 +31,7 @@ namespace OSCADSharp.ConsoleTests
                 Height = 50.8
             }.Translate(10, 5, 2);
 
-            var combined = cube.Union(cylinder);
+            var combined = cube.Difference(cylinder);
 
             Console.WriteLine(combined.ToString());
             Console.ReadKey();

OSCADSharp/OSCADSharp/Booleans/Difference.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OSCADSharp.Booleans
+{
+    /// <summary>
+    /// Subtracts the 2nd (and all further) child nodes from the first one (logical and not).    
+    /// </summary>
+    internal class Difference : BlockStatementObject
+    {
+        /// <summary>
+        /// Creates a subtraction of child nodes
+        /// </summary>
+        /// <param name="children"></param>
+        public Difference(IEnumerable<OSCADObject> children) : base("difference()", children)
+        {
+        }
+    }
+}

OSCADSharp/OSCADSharp/OSCADObject.cs

@@ -136,16 +136,32 @@ namespace OSCADSharp
         #endregion
 
         #region Boolean Operations
+        /// <summary>
+        /// Creates a union of all its child nodes. This is the sum of all children (logical or).
+        /// May be used with either 2D or 3D objects, but don't mix them.
+        /// </summary>
+        /// <param name="objects">child nodes</param>
+        /// <returns></returns>
         public OSCADObject Union(params OSCADObject[] objects)
+        {
+            return doBoolean("Union", objects, (children) => { return new Union(children); });
+        }
+
+        public OSCADObject Difference(params OSCADObject[] objects)
+        {
+            return doBoolean("Difference", objects, (children) => { return new Difference(children); });
+        }
+        
+        private OSCADObject doBoolean(string name, OSCADObject[] objects, Func<IEnumerable<OSCADObject>, OSCADObject> factory)
         {
             if (objects == null || objects.Length < 1)
             {
-                throw new ArgumentException("Union requires at least one non-null entities");
+                throw new ArgumentException(name + " requires at least one non-null entities");
             }
 
             IEnumerable<OSCADObject> children = new List<OSCADObject>() { this };
             children = children.Concat(objects);
-            return new Union(children);
+            return factory(children);
         }
         #endregion
     }

OSCADSharp/OSCADSharp/OSCADSharp.csproj

@@ -42,6 +42,7 @@
   <ItemGroup>
     <Compile Include="BlockFormatter.cs" />
     <Compile Include="BlockStatementObject.cs" />
+    <Compile Include="Booleans\Difference.cs" />
     <Compile Include="Booleans\Union.cs" />
     <Compile Include="OSCADObject.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />