gcd

Conformance: R5RS Scheme

Purpose: Compute the greatest common divisor of a sequence of numbers. This function uses Euclid's Algorithm.

Arguments:
A... - numbers

Implementation:

(define (gcd . a)
  (letrec
    ((_gcd
       (lambda (a b)
         (cond ((zero? b) a)
           ((zero? a) b)
           ((n< a b) (_gcd a (nremainder b a)))
           (else (_gcd b (nremainder a b)))))))
    (fold-left _gcd 0 (map (lambda (x)
                             (natural (abs x)))
                           a))))

Example:

(gcd 99 -77) 
=> 11

See also:
digits, expt, lcm.