lua table操作

求最大值，最小值及长度：

function maxn(t)
  local mn = nil
  for i, v in pairs(t) do 
    if (mn==nil) then
	  mn=v 
	end
    if (mn<v) then
      mn=v 
    end 
  end
  return mn
end  
function lenn(t)
  local leng=0
  for i,v in pairs(t) do
    leng=leng+1
  end
  return leng;
end 
function minn(t)
  local min=nil
  for i, v in pairs(t) do
    if (min==nil) then
      min=v
    end
    if (min>v) then
      min=v 
    end
  end
  return min
end  
tbl = {[1]=15,[2]=320,[3]=6,[25]=99,[22]=2}
print("Max:",maxn(tbl))
print("Min:", minn(tbl))
print("Length:",lenn(tbl))