local operation_stack = { ... }
local fact_pool = { ... }
local operations = { ... }

while #ops > 0 do
  local op = pop(operation_stack)
  if operations[op] then
    operations[op](operation_stack, fact_pool)
  else
    if not fact_pool[op] then fact_pool[op] = 0 end
    fact_pool[op] = fact_pool[op] + 1
  end
end