To add some more background, this is basically an attempt at fitting elements into a constrained storage space (think, e.g. printing a report, where the page size is fixed), but in a priority order.
I start with vec![false; myvec.len()];, and then basically try to fit an element. If it fits, I mark it visible, subtract from available space, and move on. Otherwise I break, or I try to fit a shorter version of that information instead.
So myvec would be something like [date_short, date_long, tab, title_short, title_long, tab, page_number, "of", total_pages];. And then I would start with showing title_long. If it fits, I set othervec[4] = true and move on to date. Otherwise I try showing title_short, and set othervec[3] = true.
Once I've finished trying to fit the elements, it would be convenient to just discard the ones I didn't use, hence this question.