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  ANSI Common Lisp   5 Data and Control Flow   5.3 Dictionary of Data and Control Flow

5.3.32 t Constant Variable

Constant Value:

The boolean representing true, and the canonical generalized boolean representing true. Although any object other than nil is considered true, t is generally used when there is no special reason to prefer one such object over another.

The symbol t is also sometimes used for other purposes as well. For example, as the name of a class, as a designator (e.g., a stream designator) or as a special symbol for some syntactic reason (e.g., in case and typecase to label the otherwise-clause).

 t   T 
 (eq t 't)  true
 (find-class 't)  #<CLASS T 610703333>
 (case 'a (a 1) (t 2))  1
 (case 'b (a 1) (t 2))  2
 (prin1 'hello t)

See Also:

Allegro CL Implementation Details:

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