Greatest common divisor: Difference between revisions

Here is an implementation using the do macro. We call the function <code>gcd2</code> so as not to conflict with <code>common-lisp:gcd</code>.

 

(do () ((zerop b) (abs a))

(shiftf a b (mod a b))))</lang>

Here is a tail-recursive implementation.

 

(gcd2 b (mod a b))))</lang>

 

The last implementation is based on the loop macro.

 

(loop for x = a then y

and y = b then (mod x y)

until (zerop y)

finally (return x)))</lang>

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