Function tryDepthFirst

tryDepthFirst<A>(zipper: Zipper.Zipper<A>): Option<Zipper.Zipper<A>>

Navigate from a node to the next node in a depth-first pre-order traversal: parents are visited before their children, and both are visited before the next sibling of the parent. For example:

For the tree:
                  ┌─┐
                  │1│
             ╭────┴─┴─────╮
           ┌─┴─┐        ┌─┴─┐
           │1.1│        │1.2│
         ╭─┴───┴╮      ╭┴───┴─╮
      ┌──┴──┐┌──┴──┐┌──┴──┐┌──┴──┐
      │1.1.1││1.1.2││1.2.1││1.2.2│
      └─────┘└─────┘└─────┘└─────┘

    tryDepthFirst ┊ result of
      called on...┊ navigation
    ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┼┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈
             “1”  ┊ some(“1.1”)
           “1.1”  ┊ some(“1.2”)
         “1.1.1”  ┊ some(“1.1.2”)
         “1.1.2”  ┊ some(“1.2”)
           “1.2”  ┊ some(“1.2.1”)
         “1.2.1”  ┊ some(“1.2.2”)
         “1.2.2”  ┊ none()

Returns Option.none when the final node in the traversal has been reached.

See depthFirst for an unsafe version.

Type Parameters

A
The underlying type of the tree.

Parameters

zipper: Zipper.Zipper<A>

Returns Option<Zipper.Zipper<A>>

An updated zipper pointing at a new focus or Option.none() if there is no next node in the depth-first traversal.

Example

import {Zipper, from, of} from 'effect-tree'
import {pipe, Option} from 'effect'

// ┬1
// ├┬2
// │├─3
// │└─4
// └┬5
//  ├─6
//  └─7
const tree = from(1, from(2, of(3), of(4)), from(5, of(6), of(7)))

const start = Zipper.fromTree(tree)

const hop1 = Zipper.tryDepthFirst(start)
const value1 = pipe(hop1, Option.map(Zipper.getValue))
expect(value1, 'hop1').toEqual(Option.some(2))

const hop2 = pipe(hop1, Option.flatMap(Zipper.tryDepthFirst))
const value2 = pipe(hop2, Option.map(Zipper.getValue))
expect(value2, 'hop2').toEqual(Option.some(3))