Task:

 Generate a string with   N   opening brackets   [   and with   N   closing brackets   ],   in some arbitrary order. 
 Determine whether the generated string is balanced; that is, whether it consists entirely of pairs of opening/closing brackets (in that order), none of which mis-nest.


Examples

   (empty)      OK
   []           OK   
   [][]         OK   
   [[][]]       OK 
   ][         NOT OK
   ][][       NOT OK
   []][[]     NOT OK



 
> use StringTools in
>       IsBalanced( "", "[", "]" );
>       IsBalanced( "[", "[", "]" );
>       IsBalanced( "]", "[", "]" );
>       IsBalanced( "[]", "[", "]" );
>       IsBalanced( "][", "[", "]" );
>       IsBalanced( "[][]", "[", "]" );
>       IsBalanced( "[[][]]", "[", "]" );
>       IsBalanced( "[[[]][]]]", "[", "]" );
>       s := Random( 20, "[]" );
>       IsBalanced( s, "[", "]" )
> end use;
                                  true
 
                                 false
 
                                 false
 
                                  true
 
                                 false
 
                                  true
 
                                  true
 
                                 false
 
                      s := "[[]][[[[[[[[[]][][]]"
 
                                 false
 