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A "variable" is a name used in a program to stand for a value.
Nearly all programming languages have variables of some sort. In the
text for a Lisp program, variables are written using the syntax for
In Lisp, unlike most programming languages, programs are represented
primarily as Lisp objects and only secondarily as text. The Lisp
objects used for variables are symbols: the symbol name is the variable
name, and the variable's value is stored in the value cell of the
symbol. The use of a symbol as a variable is independent of whether
the same symbol has a function definition. Note: Symbol Components.
The textual form of a program is determined by its Lisp object
representation; it is the read syntax for the Lisp object which
constitutes the program. This is why a variable in a textual Lisp
program is written as the read syntax for the symbol that represents the
- Global Variables
- Variable values that exist permanently, everywhere.
- Constant Variables
- Certain "variables" have values 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.
- 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.
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