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*print-radix*

∗print-radix∗ Variable

Value Type:

*print-base*—a radix . *print-radix*—a generalized boolean.

Initial Value:

The initial value of *print-base* is 10. The initial value of *print-radix* is false.

Description:

*print-base* and *print-radix* control the printing of rationals. The value of *print-base* is called the current output base.

The value of *print-base* is the radix in which the printer will print rationals. For radices above 10, letters of the alphabet are used to represent digits above 9.

If the value of *print-radix* is true, the printer will print a radix specifier to indicate the radix in which it is printing a rational number. The radix specifier is always printed using lowercase letters. If *print-base* is 2, 8, or 16, then the radix specifier used is #b, #o, or #x, respectively. For integers, base ten is indicated by a trailing decimal point instead of a leading radix specifier; for ratios, #10r is used.

Examples:

(let ((\*print-base\* 24.) (\*print-radix\* t)) 
  (print 23.)) 
▷ #24rN 
→ 23 
(setq \*print-base\* 10) → 10 
(setq \*print-radix\* nil) → NIL 
(dotimes (i 35) 
  (let ((\*print-base\* (+ i 2))) ;print the decimal number 40 
    (write 40) ;in each base from 2 to 36 
    (if (zerop (mod i 10)) (terpri) (format t " ")))) 
▷ 101000 
▷ 1111 220 130 104 55 50 44 40 37 34 
▷ 31 2C 2A 28 26 24 22 20 1J 1I 
▷ 1H 1G 1F 1E 1D 1C 1B 1A 19 18 
▷ 17 16 15 14 
→ NIL 
(dolist (pb ’(2 3 8 10 16)) 
  
  
  (let ((\*print-radix\* t) ;print the integer 10 and 
	(\*print-base\* pb)) ;the ratio 1/10 in bases 2, 
    (format t "~&~S ~S~%" 10 1/10))) ;3, 8, 10, 16 
▷ #b1010 #b1/1010 
▷ #3r101 #3r1/101 
▷ #o12 #o1/12 
▷ 10. #10r1/10 
▷ #xA #x1/A 
→ NIL

Affected By:

Might be bound by format, and write, write-to-string.

See Also:

format, write, write-to-string

Expanded Reference: *print-radix*​

Default Behavior (false)​

When *print-radix* is false, no radix specifier is printed. Numbers are printed according to *print-base*.

(let ((*print-base* 16)
      (*print-radix* nil))
  (write-to-string 255))
=> "FF"

With Radix Indicator​

When *print-radix* is true, an appropriate radix specifier is printed before rational numbers.

;; Base 16 uses #x prefix
(let ((*print-base* 16) (*print-radix* t))
  (write-to-string 255))
=> "#xFF"

;; Base 8 uses #o prefix
(let ((*print-base* 8) (*print-radix* t))
  (write-to-string 255))
=> "#o377"

;; Base 2 uses #b prefix
(let ((*print-base* 2) (*print-radix* t))
  (write-to-string 10))
=> "#b1010"

Decimal Radix Uses Trailing Dot​

For integers in base 10, the radix is indicated by a trailing decimal point rather than a leading prefix.

(let ((*print-base* 10) (*print-radix* t))
  (write-to-string 42))
=> "42."

Ratios Use #NNr Prefix for Base 10​

(let ((*print-base* 10) (*print-radix* t))
  (write-to-string 1/3))
=> "#10r1/3"

(let ((*print-base* 16) (*print-radix* t))
  (write-to-string 1/16))
=> "#x1/10"

Other Bases Use #NNr Prefix​

(let ((*print-base* 24) (*print-radix* t))
  (write-to-string 23))
=> "#24rN"