Question

Recently, Lee Baldwin showed how to write a generic, variable argument memoize function. I thought it would be better to return a simpler function where only one parameter is required. Here is my total bogus attempt:

local function memoize(f)    local cache = {}     if select('#', ...) == 1 then       return function (x)                 if cache[x] then                    return cache[x]                 else                    local y = f(x)                    cache[x] = y                    return y                 end               end    else       return function (...)                 local al = varg_tostring(...)                 if cache[al] then                    return cache[al]                 else                    local y = f(...)                    cache[al] = y                    return y                 end              end    end end 

Obviously, select('#', ...) fails in this context and wouldn’t really do what I want anyway. Is there any way to tell inside memoize how many arguments f expects?

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‘No’ is a fine answer if you know for sure. It’s not a big deal to use two separate memoize functions.

Answer 1

I guess you could go into the debug info and determine this from the source-code, but basically it’s a ‘no’, sorry.