(btree)+constructor for structure, cleaned up some code

Might as well use C++ features if I've got them

btree.cpp

@@ -18,6 +18,14 @@ struct BinaryTree
   T value;
   BinaryTree<T> *left, *right;
   enum Order (*compare)(T, T);
+  BinaryTree(T val, BinaryTree<T> *l, BinaryTree<T> *r, enum Order (*cmp)(T, T))
+  {
+    value   = val;
+    left    = l;
+    right   = r;
+    compare = cmp;
+  }
+
   ~BinaryTree()
   {
     delete left;
@@ -39,17 +47,8 @@ BinaryTree<T> *insert(BinaryTree<T> *tree, T value)
     node = &tree->right;
     break;
   }
-
-  if (*node)
-  {
-    *node = insert(*node, value);
-    return tree;
-  }
-  *node            = new BinaryTree<T>;
-  (*node)->value   = value;
-  (*node)->left    = nullptr;
-  (*node)->right   = nullptr;
-  (*node)->compare = tree->compare;
+  *node = *node ? insert(*node, value)
+                : new BinaryTree<T>(value, nullptr, nullptr, tree->compare);
   return tree;
 }
 
@@ -87,14 +86,9 @@ std::ostream &operator<<(std::ostream &ostream, const BinaryTree<T> *btree)
   return ostream;
 }
 
-void test()
-{}
-
 int main(void)
 {
-  auto tree     = new BinaryTree<int>;
-  tree->value   = 5;
-  tree->compare = [](int x, int y)
+  auto cmp = [](int x, int y)
   {
     if (x < y)
       return LT;
@@ -103,7 +97,7 @@ int main(void)
     else
       return EQ;
   };
-
+  auto tree = new BinaryTree<int>(5, NULL, NULL, cmp);
   for (int i = 0; i <= 5; ++i)
     tree = insert(tree, i * 2);