Hierarchy

Summary

Library to create, query, navigate and display hierarchy structures. You might want to read the introductory blog post.

Installing

Using

After having created a hierarchy with hierarchy-new, populate it by calling hierarchy-add-tree or hierarchy-add-trees. You can then optionally sort its element with hierarchy-sort. For example, you can create an animal hierarchy by passing a child-to-parent function to hierarchy-add-tree:

(require 'hierarchy)

(setq animals (hierarchy-new))

(let ((parentfn
       ;; Given an item, return its parent
       (lambda (item)
         (cl-case item
           (dove 'bird)
           (pigeon 'bird)
           (bird 'animal)
           (dolphin 'animal)
           (cow 'animal)))))
  (hierarchy-add-tree animals 'dove parentfn)
  (hierarchy-add-tree animals 'pigeon parentfn)
  (hierarchy-add-tree animals 'dolphin parentfn)
  (hierarchy-add-tree animals 'cow parentfn))

(hierarchy-sort animals)

You can learn more about your hierarchy by using functions such as hierarchy-roots, hierarchy-length, hierarchy-children, hierarchy-descendant-p. For example, hierarchy-roots returns any item without a parent in a hierarchy:

(hierarchy-roots animals)

animal

animal is the only item of the animals hierarchy with no parent. To get all items with no child, use hierarchy-leafs:

(hierarchy-leafs animals)

dove

pigeon

dolphin

cow

It is possible to get the children of an item by using hierarchy-children:

(hierarchy-children animals 'animal)

bird

cow

dolphin

We see here that animal has three children.

You can navigate a hierarchy using hierarchy-map-item, hierarchy-map and hierarchy-map-tree. For example, this code inserts a text view of a hierarchy in a buffer:

(with-temp-buffer
  (hierarchy-map
   (hierarchy-labelfn-indent
    (lambda (animal _) (insert (symbol-name animal) "\n")))
   animals)
  (buffer-substring (point-min) (point-max)))

animal
  bird
    dove
    pigeon
  cow
  dolphin

The indentation between a parent and its child can be configured by passing one more parameter to hierarchy-labelfn-indent. You can also display clickable buttons instead of just plain text using either hierarchy-labelfn-button or hierarchy-labelfn-button-if.

If you want a buffer containing only a hierarchy while being able to navigate it with standard key-bindings use either hierarchy-tabulated-display or hierarchy-tree-display as shown in below animated pictures.

(switch-to-buffer
 (hierarchy-tabulated-display
  animals
  (hierarchy-labelfn-indent
   (hierarchy-labelfn-button
    (lambda (item _) (insert (symbol-name item)))
    (lambda (item _) (message "You clicked on: %s" item))))))

(switch-to-buffer
 (hierarchy-tree-display
  animals
  (lambda (item _) (insert (symbol-name item)))))

Examples

File-system example

The hierarchy library can be used to display any kind of hierarchy you need. For example, a file-system navigator is provided as an example.

(load "./examples/hierarchy-examples-fs.el")

;; Execute one of the following lines to show the `.emacd.d' hierarchy
;; in either a tabulated list or a tree widget. This takes around 3
;; seconds on my computer.

(hierarchy-examples-fs-display-filesystem "~/.emacs.d")

(hierarchy-examples-fs-display-filesystem-tree "~/.emacs.d")

Faces hierarchy example

Emacs and packages define quite a lot of faces. Because a face may inherit from another one, we can get a hierarchy of them:

This is based on an idea and code from Yuan Fu.

Major modes hierarchy example

Emacs and packages define quite a lot of major modes. A major mode usually derives from another one which means we can get a hierarchy of major modes:

Class hierarchy example

With a bit more work, the hierarchy library can also be used to display class hierarchies (as I am currently experimenting in this project).

WammKD/hierarchy