W3cubDocs

Variables

A variable is a name used in a program to stand for a value. In Lisp, each variable is represented by a Lisp symbol (see Symbols). The variable name is simply the symbol’s name, and the variable’s value is stored in the symbol’s value cell⁸. See Symbol Components. In Emacs Lisp, the use of a symbol as a variable is independent of its use as a function name.

As previously noted in this manual, a Lisp program is represented primarily by Lisp objects, and only secondarily as text. The textual form of a Lisp program is given by the read syntax of the Lisp objects that constitute the program. Hence, the textual form of a variable in a Lisp program is written using the read syntax for the symbol representing the variable.

• Global Variables:		Variable values that exist permanently, everywhere.
• Constant Variables:		Variables that never change.
• Local Variables:		Variable values that exist only temporarily.
• Void Variables:		Symbols that lack values.
• Defining Variables:		A definition says a symbol is used as a variable.
• Tips for Defining:		Things you should think about when you define a variable.
• Accessing Variables:		Examining values of variables whose names are known only at run time.
• Setting Variables:		Storing new values in variables.
• Watching Variables:		Running a function when a variable is changed.
• Variable Scoping:		How Lisp chooses among local and global values.
• Buffer-Local Variables:		Variable values in effect only in one buffer.
• File Local Variables:		Handling local variable lists in files.
• Directory Local Variables:		Local variables common to all files in a directory.
• Connection Local Variables:		Local variables common for remote connections.
• Variable Aliases:		Variables that are aliases for other variables.
• Variables with Restricted Values:		Non-constant variables whose value can not be an arbitrary Lisp object.
• Generalized Variables:		Extending the concept of variables.