parse.vim

function! s:parse_up_to_prime(pushers, poppers, acc, ele)
  let [l:result, l:count] = a:acc
  " run through case
  if l:count < 0
    return a:acc
  endif

  call lab42#test#dbg_many(a:ele, a:poppers)
  let l:increment = ( index(a:pushers, a:ele) >= 0 ? 1 : 0)
  let l:increment = ( index(a:poppers, a:ele) >= 0 ? -1 : l:increment)
  return [l:result . a:ele, l:count + l:increment]
endfunction