example.lua

-- With select('#') and recursion
do
  local function _tsa(n,a,...)
    if n > 0 then
      return tostring(a),_tsa(n-1,...)
    end
  end
  
  function tostringall(...)
    local n = select('#',...)
    if n > 0 then
      return _tsa(n,...)
    end
  end
end

-- With an array
do
  function tostringall(...)
    local n = select('#',...)
    local s = {...}
    for i = 1,n do
      s[i] = tostring(s[i])
    end
    return unpack(s,1,n)
  end
end

-- Note that you need to explicitly check how many values were passed with
-- select('#'...). #{...} is undefined if `...` contains nils