procedure main()
    aTree := [1, [2, [4, [7]], [5]], [3, [6, [8], [9]]]]
    bTree := [1, [2, [4, [7]], [5]], [3, [6, [8], [9]]]]
    write("aTree and bTree ",(sameFringe(aTree,bTree),"have")|"don't have",
          " the same leaves.")
    cTree := [1, [2, [4, [7]], [5]], [3, [6, [8]]]]
    dTree := [1, [2, [4, [7]], [5]], [3, [6, [8], [9]]]]
    write("cTree and dTree ",(sameFringe(cTree,dTree),"have")|"don't have",
          " the same leaves.")
end

procedure sameFringe(a,b)
    return same{genLeaves(a),genLeaves(b)}
end

procedure same(L)
   while n1 := @L[1] do {
      n2 := @L[2] | fail
      if n1 ~== n2 then fail
      }
   return not @L[2]
end

procedure genLeaves(t)
    suspend (*(node := preorder(t)) == 1, node[1])
end

procedure preorder(L)
    if \L then suspend L | preorder(L[2|3])
end