How do I write a generic memoize function?

Question

I\'m writing a function to find triangle numbers and the natural way to write it is recursively:

function triangle (x)
   if x == 0 then return 0 end
   retu         


        

Answer 1

function memoize (f)
   local cache = {}
   return function (x)
             if cache[x] then
                return cache[x]
             else
                local y = f(x)
                cache[x] = y
                return y
             end
          end
end

triangle = memoize(triangle);

Note that to avoid a stack overflow, triangle would still need to be seeded.