Source code in the icon programming language

link numbers   # gcd is part of the Icon Programming Library
procedure main(args)
    write(gcd(arg[1], arg[2])) | "Usage: gcd n m")
end


procedure gcd(i,j)		#: greatest common divisor
   local r

   if (i | j) < 1 then runerr(501)

   repeat {
      r := i % j
      if r = 0 then return j
      i := j
      j := r
      }
end