to enhance jaytea's post:

each work with a dynamic number of parameters

alias gcd {
  while $2 {
    while $2 {
      tokenize 32 $2 $calc($1 % $2) $3-
    }
    tokenize 32 $1 $3-
  }
  return $1
}

alias lcm {
  while $2 {
    tokenize 32 $calc($1 * $2 / $gcd($1, $2)) $3-
  }
  return $1
}