link sets

procedure main ()
  a := set(1, 1, 2, 3, 4)
  b := set(2, 3, 5)
  write ("a: ", simage(a))
  write ("b: ", simage(b))
  # basic set operations
  write ("Intersection: ", simage (a**b))
  write ("Union: ", simage        (a++b))
  write ("Difference: ", simage   (a--b))
  # membership
  if member(a, 2) then
    write ("2 is a member of a")
  else
    write ("2 is not a member of a")
  if member(a, 5) then
    write ("5 is a member of a")
  else
    write ("5 is not a member of a")
  # equality
  if seteq(a, set(1,2,3,4,4)) then
    write ("a equals set(1,2,3,4,4)")
  else
    write ("a does not equal set(1,2,3,4,4)")
  if seteq(a, b) then
    write ("a equals b")
  else
    write ("a does not equal b")
  # check subset
  if setlt(set(1,2), a) then
    write ("(1,2) is included in a")
  else
    write ("(1,2) is not included in a")
  if setlt(a, set(1,2,5), a) then
    write ("(1,2,5) is included in a")
  else
    write ("(1,2,5) is not included in a")
end