go1 ?=>
  tests(Tests),
  member(Test,Tests),
  printf("%s: ", Test),
  (  balanced_brackets(Test) ->
       println("OK")
     ;
       println("NOT OK")
  ),
  fail,
  nl.
go1 => true.

% Check if a string of [] is balanced
balanced_brackets(B) =>
   C = 0,
   foreach(I in 1..B.length, C >= 0)
      C:= C + cond(B[I] = '[', 1, -1)
   end,
   C == 0.

tests(["","[]", "[][]", "[[][]]", "][",
       "][][", "[]][[]", "[][][][][][][][][][]",
       "[[[[[[[]]]]]]]", "[[[[[[[]]]]]]",
       "[][[]][]","[[][]][]", "[][][[]][]"]).