Problem Statement

Compute the   least common multiple   (LCM)   of two integers. Given   m   and   n,   the least common multiple is the smallest positive integer that has both   m   and   n   as factors.

The least common multiple of   12   and   18   is   36,       because:

As a special case,   if either   m   or   n   is zero,   then the least common multiple is zero.

One way to calculate the least common multiple is to iterate all the multiples of   m,   until you find one that is also a multiple of   n. If you already have   gcd   for greatest common divisor,   then this formula calculates   lcm.

One can also find   lcm   by merging the prime decompositions of both   m   and   n.

Let's start with the solution:

/* Calculate the Least Common Multiple of two integers. */

LCM: procedure options (main);          /* 16 October 2013 */
   declare (m, n) fixed binary (31);

   get (m, n);
   put edit ('The LCM of ', m, ' and ', n, ' is', LCM(m, n)) (a, x(1));

LCM: procedure (m, n) returns (fixed binary (31));
   declare (m, n) fixed binary (31) nonassignable;

   if m = 0 | n = 0 then return (0);
   return (abs(m*n) / GCD(m, n));
end LCM;

GCD: procedure (a, b) returns (fixed binary (31)) recursive;
   declare (a, b) fixed binary (31);

   if b = 0 then return (a);

   return (GCD (b, mod(a, b)) );

end GCD;
end LCM;