Learning Emacs Lisp

Table of Contents

1. 1. List Processing
   1. 1.1. Lisp List
   2. 1.2. Run a Program
   3. 1.3. Generate an Error Message
   4. 1.4. Functions and Arguments
   5. 1.5. The message function
   6. 1.6. Setting the Value of a Variable
2. 2. Practicing Evaluation
3. 3. How to Write Function Definitions
   1. 3.1. The defun Macro

List Processing

Lisp List

• List definition: '(a, b, c, d, ...)
• lists can be programs AND data
• Atom: indivisible element
• Atoms contain: numbers, symbols, …

  Run a Program

• ' tells List to do nothing with the list, otherwise, use the first element in the list as the function
• Use C-x C-e to evaluate a lisp expression in emacs

  Generate an Error Message

• Evaluate (a, b, c, d) will generate an error, type q to quit

  Functions and Arguments

• concat number-to-string

  The message function

• (message "This is a message")
• (message "The current buffer is %s" (buffer-name))

  Setting the Value of a Variable

• Using set: (set 'flowers '(rose violet daisy buttercup))
• Using setq: (setq flowers '(rose violet daisy buttercup))

  Practicing Evaluation

• To view documentation: (info "(elisp)Files")
• Each keystroke calls the self-insert-command, an interactive function
• (buffer-size) (point)

  How to Write Function Definitions

  The defun Macro

• A typical list function:

(defun function_name (args)
"documentation"
(interactive argument-passing-info) ; optional
body...)

• interactive: (interactive "p") uses prefix
• let:

(let ((var_name, var_value),
      (var_name, var_value)...)
      body...
)

• if:

(if (> 5 4)
(message "5 is greater than 4")
(message "otherwise"))

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