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Allegro CL
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  ANSI Common Lisp   10 Symbols   10.2 Dictionary of Symbols

10.2.1 symbol System Class

Class Precedence List:
symbol, t

Symbols are used for their object identity to name various entities in Common Lisp, including (but not limited to) linguistic entities such as variables and functions.

Symbols can be collected together into packages. A symbol is said to be interned in a package if it is accessible in that package; the same symbol can be interned in more than one package. If a symbol is not interned in any package, it is called uninterned.

An interned symbol is uniquely identifiable by its name from any package in which it is accessible.

Symbols have the following attributes. For historical reasons, these are sometimes referred to as cells, although the actual internal representation of symbols and their attributes is implementation-dependent.

Operations on a symbol's value cell and function cell are sometimes described in terms of their effect on the symbol itself, but the user should keep in mind that there is an intimate relationship between the contents of those cells and the global variable or global function definition, respectively.

Symbols are used as identifiers for lexical variables and lexical function definitions, but in that role, only their object identity is significant. Common Lisp provides no operation on a symbol that can have any effect on a lexical variable or on a lexical function definition.

See Also:
Section 2.3.4 Symbols as Tokens, Section Potential Numbers as Tokens, Section Printing Symbols

Allegro CL Implementation Details:

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