Comments on: Implementing Memoize in Delphi 2009

By: Craig Stuntz’s Weblog : My CodeRage Presentation: Functional Programming in Delphi 2009

Tue, 04 Nov 2008 20:23:10 +0000

[...] you’ve been following my blog over the past few months, you might have a fair idea of what to expect. As you can tell from the somewhat vague abstract, I’m still rounding out the details of [...]

By: Craig Stuntz

Craig Stuntz — Fri, 03 Oct 2008 12:52:59 +0000

Thanks, Allen, Prapin, and Kryvich. Kryvich, I think that would work. I haven’t tested to make sure the "inner" Result doesn’t get confused with the outer Result, but it’s a bug if your version doesn’t work, IMHO.

By: Kryvich

Kryvich — Fri, 03 Oct 2008 06:12:02 +0000

I like it too!

Just 1 question. Is it possible to write it as below:

Result := function(arg: A): R
begin
if not Map.TryGetValue(arg, Result) then begin
Result := AFunc(arg);
Map.Add(arg, Result);
end;
end;

It’s a rather shorter.

By: Prapin

Prapin — Thu, 02 Oct 2008 01:25:48 +0000

Cool!

By: Allen Bauer

Allen Bauer — Wed, 01 Oct 2008 19:48:40 +0000

This is excellent. Yet another really cool use for anonymous methods! Another minor optimization you can do is to add the "static" directive to your generic class method. That will remove the implicit "Self" parameter to the function since it is clearly not needed. (Self in the case of a class method is a reference to the class *type*). By adding "static" it makes the method merely a scoped global procedure or function.

This will remove the added (I know, it’s very, very minor) overhead of the MOV EAX, for the call to TMemoize.Memoize(). Since your goal was a performance boost, might as well grab all you can :-).

Allen.