Elisp: What's “feature”?

By Xah Lee. Date: . Last updated: .

Emacs's Concept of Feature

For example, type Alt+x describe-variable Enter ↵ features Enter ↵. You'll see something like this:

ibuffer etags ring cc-mode cc-fonts cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs xlsl-mode encoded-kb speck sgml-mode dired info newcomment desktop recentf tree-widget wid-edit advice help-fns …

require and provide

The purpose of features is for emacs to know if a package is already loaded.

The features variable and the functions {provide, require}, is the mechanism.

The require function checks the features variable to see if a symbol is already there, if not, then load the file.

The provide function adds a symbol to the features list.

back to Elisp: require, load, load-file, autoload, feature, Explained

Writing Major Mode

  1. How to Write a Emacs Major Mode for Syntax Coloring
  2. Elisp: html6-mode
  3. Elisp: Font Lock Mode Basics
  4. Elisp: How to Define Face
  5. Elisp: How to Color Comment in Major Mode
  6. Elisp: How to Write Comment Command in Major Mode
  7. Elisp: How to Write Your Own Comment Command from Scratch
  8. Elisp: How to Write Keyword Completion Command
  9. Elisp: How to Create Keymap for Major Mode
  10. Elisp: Create Abbrev and Templates for Major Mode
  11. Elisp: Text Properties
  12. Elisp: Overlay Highlighting
  13. Emacs: Lookup Google, Dictionary, Documentation
  14. Elisp: Syntax Table Tutorial

  1. Elisp: How to Name Your Major Mode
  2. Elisp: What's “feature”?
  3. Elisp: require, load, load-file, autoload, feature, Explained

Syntax Table

  1. Elisp: Syntax Table Tutorial
  2. Elisp: How to Find Syntax of a Character?
  3. Elisp: How to Modify Syntax Table Temporarily
  4. Elisp: How to Determine If Cursor is Inside String or Comment
  5. Elisp: Regex Patterns and Syntax Table
  6. Elisp: Find Matching Bracket Character
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