Std.Tree.foldTree

fn

This is a callable function.

What it does

Each node combined with what its children answered.

The general fold over this shape, and the one the others are special cases

of: size is a fold that adds one to the sum below, height is a fold that

adds one to the largest, preorder is a fold that prepends. A node is given

its own value and the answers from beneath it, so anything that depends on a

subtree can be written without a second walk.

Read the signature

• The text after the name is the type checked by Pudu.
• Read arrows from left to right: inputs come first, and the final type is returned.
• & borrows a value for this call instead of moving or copying it.
• Names inside [ ] are type arguments, such as the item type held by a collection.