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ANSI Common Lisp  4 Types and Classes 4.4 Dictionary of Types and Classes
- Supertypes:
-
boolean,
symbol,
t
- Description:
-
The type boolean contains the symbols t and nil,
which represent true and false, respectively.
- See Also:
-
t (constant variable),
nil (constant variable),
if,
not,
complement
- Notes:
-
Conditional operations, such as if,
permit the use of generalized booleans,
not just booleans;
any non-nil value,
not just t,
counts as true for a generalized boolean.
However, as a matter of convention,
the symbol t is considered the canonical value to use
even for a generalized boolean when no better choice presents itself.
- Allegro CL Implementation Details:
-
None.
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