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Programming in Emacs Lisp

3. How To Write Function Definitions

When the Lisp interpreter evaluates a list, it looks to see whether the first symbol on the list has a function definition attached to it; or, put another way, whether the symbol points to a function definition. If it does, the computer carries out the instructions in the definition. A symbol that has a function definition is called, simply, a function (although, properly speaking, the definition is the function and the symbol refers to it.)

An Aside about Primitive Functions
3.1 The defun Special Form		The defun special form.
3.2 Install a Function Definition		Install a function definition.
3.3 Make a Function Interactive		Making a function interactive.
3.4 Different Options for interactive		Different options for interactive.
3.5 Install Code Permanently		Installing code permanently.
3.6 let		Creating and initializing local variables.
3.7 The if Special Form		What if?
3.8 If--then--else Expressions		If--then--else expressions.
3.9 Truth and Falsehood in Emacs Lisp		What Lisp considers false and true.
3.10 save-excursion		Keeping track of point, mark, and buffer.
3.11 Review
3.12 Exercises