Re: Learning Lua

[Tom N Harris <telliamed@...>]

On 9/17/2010 6:58 AM, Luiz Henrique de Figueiredo wrote:
> local cache={}
> function mesure(x)
> 	local y=cache[x]
> 	if y==nil then
> 		if x==1 then
> 			y=0
> 		elseif x%2==0 then
> 			y=1+mesure(x/2)
> 		else
> 			y=1+mesure(3*x+1)
> 		end
> 		cache[x]=y
> 	end
> 	return y
> end

As a metamethod....

local mesure = setmetatable({0}, {
  __index = function(t,n)
    local y
    if n%2==0 then
      y=1+t[n/2]
    else
      y=1+t[3*n+1]
    end
    t[n]=y
    return y
  end})
for i=1,1000000 do
  length = mesure[i]
  -- etc.
end

--
- tom
telliamed@whoopdedo.org