lua 将数字转成字符串

function numToString(mystr)
    local resuilt =''
    for i=1,#mystr,1 do
        local strCharNum= string.sub(mystr,i,i)
        --print(strCharNum)
        local strCharAsc=string.byte(strCharNum)+ 48
        --print(strCharAsc)
        local strCharStr= string.char(strCharAsc)
        resuilt = resuilt .. strCharStr

    end
    return resuilt
end

字符串好像没有索引