From: Mathieu Bouchard <matju@...>
Date: 2001-11-22T16:15:02+09:00
Subject: [ruby-talk:26119] Re: call_myself


On Thu, 22 Nov 2001, Tobias Reif wrote:
> --- the example we all know---
> def fact(n)
>    if n == 0
>      1
>    else
>      n * fact(n-1)
>    end
> end
> -------------------
> Is there something that makes it clear that the method calls itself?

It's better for a method not to explicitly call itself, because that way
you can insert a method between that method and itself. e.g.:

$fact_cache = []
alias orig_fact
def fact(n)
  $fact_cache[n] ||= orig_fact(n)
end

which is not a speed improvement on the first time, but it is on
subsequent times. For functions like fibonacci (the other classic
example) it's always a tremendous speed improvement (exponential vs
linear)

Robert has written a package (memoize) for that. iirc it's much like what
Mark Jason Dominus has done on the Perl side.

There are other interesting things you can do by "inserting" a method like
that (e.g. printing the function call tree)

________________________________________________________________
Mathieu Bouchard                   http://hostname.2y.net/~matju