Luaatoi解析：字符串转整数的边界处理

local function toInt(s)
    local n = 0
    for i = 1, #s do
        local b = s:byte(i)
        if b < 48 or b > 57 then return nil end
        n = n * 10 + (b - 48)
    end
    return n
end

local function atoi(s)
    local i, sign = 1, 1
    while s:byte(i) == 32 do i = i + 1 end
    if s:byte(i) == 45 then sign, i = -1, i + 1
    elseif s:byte(i) == 43 then i = i + 1 end
    local n = 0
    while i <= #s do
        local b = s:byte(i)
        if b < 48 or b > 57 then break end
        n = n * 10 + (b - 48)
        i = i + 1
    end
    return sign * n
end
local p = getplayerbyname("atoi01")
sendmsg(p, 1, atoi("  -728 元"))