Tree

The Tree component provides immutable tree data structures and operations for hierarchical data manipulation.

Trees are fundamental data structures for representing hierarchical relationships. This component provides immutable tree nodes (LeafNode and TreeNode), pure constructor functions, functional operations (map, filter, reduce, fold), tree traversal algorithms, and search utilities.

Design

The Tree component has a simple design:

• NodeInterface<T>: Base interface with getValue(): T
• LeafNode<T>: Leaf nodes (no children)
• TreeNode<T>: Tree nodes with getChildren(): list<NodeInterface<T>>

All tree operations are immutable -- they return new trees rather than modifying existing ones.

Usage

Building Trees

Use the tree() and leaf() constructor functions to build trees:

@example('collections/tree-building.php')

You can also build trees from nested arrays or flat lists with parent references, which is especially useful for database records:

@example('collections/tree-from-data.php')

Transforming Trees

@example('collections/tree-transforming.php')

Traversal

Three traversal orders are available:

@example('collections/tree-traversal.php')

Searching and Paths

@example('collections/tree-searching.php')

Custom Serialization

The traverse() function gives you full control over how the tree is serialized:

@example('collections/tree-serialization.php')

See src/Psl/Tree/ for the full API.