Macro tree 

macro_rules! tree {
    ($($tt:tt)*) => { ... };
}

A macro that evaluates to the root node of a new tree of type Tree.

Syntax is simple:

• For non-root nodes:
  • data to describe a leaf node.
  • (data, [descendants_recursive]) to describe a node with descendants.
• For the root node:
  • data to describe single node tree.
  • data, [descendants_recursive] to describe a tree with descendants.

See tree_node macro for usage examples.