====== Trees binary ======
{{tag>trees}}
===== Description =====
Defining binary trees.

**Source**:  The Art of Prolog
===== Download =====
Program source code: {{trees_binary.pl}}
===== Listing =====
<code prolog>
/*
	binary_tree(Tree) :- Tree is a binary tree.
*/
	binary_tree(void).
	binary_tree(tree(Element,Left,Right)) :-
		binary_tree(Left), binary_tree(Right).

%	Program 3.23: Defining binary trees
</code>
===== Comments =====