From: Intransition <transfire@...>
Date: 2010-08-24T10:51:49+09:00
Subject: Re: Your thoughts on #memo ?



On Aug 23, 12:47 pm, Caleb Clausen <vikk...@gmail.com> wrote:
> On 8/23/10, Intransition <transf...@gmail.com> wrote:
>
> > The use case for #memo is an alternative to:
>
> >   def m
> >     @m ||= ....
> >   end
>
> > But differs in that it avoids the need for an instance variable. I
> > tend to use the "@m ||=" idiom a lot, though I wonder about it's
> > threading implications, and whether something like #memo would be more
> > robust.
>
> Your #memo method is no more re-entrant than the instance variable
> example you gave above. If you want it to be re-entrant, you need to
> have a mutex.

Ah, thanks Caleb. So to be on the "safe" side I will have to use a
mutex for any memoization code I might devise --there's no way around
it.

> Also, I seem to recall that methods defined via define_method are
> slower than methods defined via def. But I couldn't see a way to
> rewrite your code using def instead...

Well, speed wise, I imagine the mutex will really take care of
that ;-)