*print-pretty*

∗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 whitespace₁ is output when printing an expression.

If it is true, the pretty printer is used, and the Lisp printer will endeavor to insert extra whitespace₁ 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 "~%~S " x) 
	   (terpri) (princ x) (princ " ") 
	   (format t "~%~A " x)))) 
  (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

Expanded Reference: *print-pretty*

tip

TODO: Please contribute to this page by adding explanations and examples

*print-pretty*