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



String method: isBalanced
| c |
   0 self forEach: c [ 
      c '[' == ifTrue: [ 1+ continue ]
      c ']' <> ifTrue: [ continue ]
      1- dup 0 < ifTrue: [ drop false return ]
      ]
   0 == ;
 
: genBrackets(n)
   "" #[ "[" "]" 2 rand 2 == ifTrue: [ swap ] rot + swap + ] times(n) ;