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



import datatypes as dt
 
fn is_valid(bracket string) bool {
    mut s := dt.Stack<string>{}
    for b in bracket.split('') {
        if b == '[' {
            s.push(b)
        } else {
            if s.peek() or {''} == '[' {
                s.pop() or {panic("WON'T GET HERE EVER")}
            } else {
                return false
            }
        }
    }
    return true
}
 
fn main() {
    brackets := ['','[]','[][]','[[][]]','][','][][','[]][[]','[][[][[]][][[][]]]']
    for b in brackets {
        println('$b ${is_valid(b)}')
    }
}