#### 22.4.26 *print-pretty* [Variable] ¶

#### Value Type:: ¶

a generalized boolean.

#### Initial Value:: ¶

implementation-dependent.

#### Description:: ¶

Controls whether the Lisp printer calls the pretty printer.

If it is false, the pretty printer is not used and

a minimum

of whitespace_1 is output when printing an expression.

If it is true, the pretty printer is used, and the Lisp printer will endeavor to insert extra whitespace_1 where appropriate to make expressions more readable.

*print-pretty* has an effect even when the value of *print-escape* is false.

#### Examples:: ¶

     (setq *print-pretty* 'nil) ⇒  NIL
     (progn (write '(let ((a 1) (b 2) (c 3)) (+ a b c))) nil)
     |>  (LET ((A 1) (B 2) (C 3)) (+ A B C))
    ⇒  NIL
     (let ((*print-pretty* t))
       (progn (write '(let ((a 1) (b 2) (c 3)) (+ a b c))) nil))
     |>  (LET ((A 1)
     |>        (B 2)
     |>        (C 3))
     |>    (+ A B C))
    ⇒  NIL
    ;; Note that the first two expressions printed by this next form
    ;; differ from the second two only in whether escape characters are printed.
    ;; In all four cases, extra whitespace is inserted by the pretty printer.
     (flet ((test (x)
              (let ((*print-pretty* t))
                (print x)
                (format t "~
                (terpri) (princ x) (princ " ")
                (format t "~
      (test '#'(lambda () (list "a" #'c #'d))))
     |>  #'(LAMBDA ()
     |>      (LIST "a" #'C #'D))
     |>  #'(LAMBDA ()
     |>      (LIST "a" #'C #'D))
     |>  #'(LAMBDA ()
     |>      (LIST a b 'C #'D))
     |>  #'(LAMBDA ()
     |>      (LIST a b 'C #'D))
    ⇒  NIL

#### See Also:: ¶

write, prin1, print, pprint, princ [Function]