var y = 0; //a global to keep track of state
//does not need closures for this to work yet

fun next(x) {
    if (x == 10)
    {
        y = y + 1;
        x = 0;
    }
    if (y == 10)
        return -1;
    return x+y+1;
}

var i = 0;
for (; i != -1; i = next(i))
    print(i);
// before using next
//output:0
// y = 0
//output:1
//output:2
//output:3
//output:4
//output:5
//output:6
//output:7
//output:8
//output:9
//output:10
// y = 1
//output:2
//output:3
//output:4
//output:5
//output:6
//output:7
//output:8
//output:9
//output:10
// y = 2
//output:3
//output:4
//output:5
//output:6
//output:7
//output:8
//output:9
//output:10
// y = 3
//output:4
//output:5
//output:6
//output:7
//output:8
//output:9
//output:10
// y = 4
//output:5
//output:6
//output:7
//output:8
//output:9
//output:10
// y = 5
//output:6
//output:7
//output:8
//output:9
//output:10
// y = 6
//output:7
//output:8
//output:9
//output:10
// y = 7
//output:8
//output:9
//output:10
// y = 8
//output:9
//output:10
// y = 9
//output:10
// y = 10