Lua调度场进阶：带括号的完整转换

-- 错误：括号当普通记号进栈，右括号无人处理
for _, tk in ipairs(tokens) do
    ops[#ops + 1] = tk
end

local PRI = {["+"] = 1, ["-"] = 1, ["*"] = 2, ["/"] = 2}
local function toRPN(tokens)
    local out, ops = {}, {}
    for _, tk in ipairs(tokens) do
        if tonumber(tk) then
            out[#out + 1] = tonumber(tk)
        elseif tk == "(" then
            ops[#ops + 1] = tk
        elseif tk == ")" then
            while ops[#ops] ~= "(" do
                out[#out + 1] = table.remove(ops)
            end
            table.remove(ops)
        else
            while ops[#ops] ~= nil
                and ops[#ops] ~= "("
                and PRI[ops[#ops]] >= PRI[tk] do
                out[#out + 1] = table.remove(ops)
            end
            ops[#ops + 1] = tk
        end
    end
    while #ops > 0 do
        out[#out + 1] = table.remove(ops)
    end
    return out
end
local function evalRPN(rpn)
    local st = {}
    for _, tk in ipairs(rpn) do
        if type(tk) == "number" then
            st[#st + 1] = tk
        else
            local b = table.remove(st)
            local a = table.remove(st)
            if tk == "+" then st[#st + 1] = a + b end
            if tk == "-" then st[#st + 1] = a - b end
            if tk == "*" then st[#st + 1] = a * b end
            if tk == "/" then st[#st + 1] = a / b end
        end
    end
    return st[1]
end
local expr = {"(", "2", "+", "3", ")", "*", "4"}
local label = panel:getChildByName("calcText")
label:setString(tostring(evalRPN(toRPN(expr))))