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elisp: Variables

 
 11 Variables
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 A “variable” is a name used in a program to stand for a value.  In Lisp,
 each variable is represented by a Lisp symbol (Symbols).  The
 variable name is simply the symbol’s name, and the variable’s value is
 stored in the symbol’s value cell(1).  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.
 

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· 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.
· 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.
· 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.
 
    ---------- Footnotes ----------
 
    (1) To be precise, under the default “dynamic scoping” rule, the
 value cell always holds the variable’s current value, but this is not
 the case under the “lexical scoping” rule.  Variable Scoping,
 for details.
 

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