<br />
<b>Warning</b>:  session_start(): open(/var/lib/php/sessions/sess_gndaqjg0i1pf5o48tes74mkmd2, O_RDWR) failed: No space left on device (28) in <b>/var/www/tb-usercake/models/config.php</b> on line <b>51</b><br />
<br />
<b>Warning</b>:  session_start(): Failed to read session data: files (path: /var/lib/php/sessions) in <b>/var/www/tb-usercake/models/config.php</b> on line <b>51</b><br />
-- simple PN math evaluator
-- expects input in "input"

tokens = {}
for token in string.gmatch(input, "[^%s]+") do
  table.insert(tokens, token)
end

stack = {}

function push(x) table.insert(stack, x) end
function pop() local x = stack[#stack]; stack[#stack] = nil; return x end

for i = #tokens, 1, -1 do
  token = tokens[i]
  if token:match('^[0-9]+$') then
    push(tonumber(token))
  else
    arg1 = pop()
    arg2 = pop()
    if token == '+' then
      push(arg1+arg2)
    elseif token == '*' then
      push(arg1*arg2)
    else
      error("Unknown operation: "..token)
    end
  end
end

return pop()