digit-char-p char &optional radix → weight

char — a character.

radix — a radix. The default is 10.

weight — either a non-negative integer less than radix, or false.

Tests whether char is a digit in the specified radix (i.e., with a weight less than radix). If it is a digit in that radix, its weight is returned as an integer; otherwise nil is returned.

(digit-char-p #\5)    → 5 
(digit-char-p #\5 2)  → false 
(digit-char-p #\A)    → false 
(digit-char-p #\a)    → false 
(digit-char-p #\A 11) → 10 
(digit-char-p #\a 11) → 10 
(mapcar #'(lambda (radix) 
            (map 'list #'(lambda (x) (digit-char-p x radix)) 
                 "059AaFGZ")) 
        '(2 8 10 16 36)) 
→ ((0 NIL NIL NIL NIL NIL NIL NIL) 
    (0 5 NIL NIL NIL NIL NIL NIL) 
    (0 5 9 NIL NIL NIL NIL NIL) 
    (0 5 9 10 10 15 NIL NIL) 
    (0 5 9 10 10 15 16 35))

None. (In particular, the results of this predicate are independent of any special syntax which might have been enabled in the current readtable.)

alphanumericp

Digits are graphic characters.