normalize

Conformance: SketchyLISP Core

Purpose: Normalize a number by removing leading zeroes and plus signs.

Arguments:
X - number

Implementation:

(define (normalize x)
  (letrec
    ; remove leading zeroes from natural number
    ((skip0
       (lambda (x)
         (cond ((null? (cdr x)) x)
           ((eq? (car x) 0d)
             (skip0 (cdr x)))
           (else x))))
     (norm
       (lambda (x)
         (cond ((eq? (car x) '+)
             (skip0 (cdr x)))
           ((eq? (car x) '-)
             (let ((d (skip0 (cdr x))))
               (cond ((equal? d '(0d)) d)
                 (else (cons '- d)))))
           (else (skip0 x))))))
    (list->integer
      (norm (integer->list x)) #t)))

Example:

(normalize +000511) 
=> 511

See also:
digits, ndivide.