*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::

@xref{write; prin1; print; pprint; princ}

Go to the first, previous, next, last section, table of contents.