Re: Visitor pattern vs if-ladder

From:

Patricia Shanahan <pats@acm.org>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 23 Apr 2009 09:20:08 -0700

Message-ID:

<O_SdnccX7JShCG3UnZ2dnUVZ_tmdnZ2d@earthlink.com>

Philipp wrote:

On Apr 23, 4:05 pm, Patricia Shanahan <p...@acm.org> wrote:

<snip lots of very good counting strategies>

I'm sure there are more ways of doing this. I don't think I know enough
about the real case to have an informed opinion on which I would use.

Sorry if my post wasn't clear. I don't really want to count anything.
I just made up this for the sake of measuring the speed difference
between using a ladder and the visitor pattern.

In my real code the actions which are taken for each subclass are much
more complicated and depend on other classes. (see my answer to Lew)

But counting does make a good case for illustrating the extent to which
it is worth looking for other strategies, rather than just considering
two not entirely satisfactory alternatives.

I don't think measuring speed differences on an artificial problem makes
any sense with current processors. Performance is usually dominated by
cache misses and branch prediction failures, and those depend a lot on
context. The relative speed may be significantly different, in either
direction, for your real problem.

Patricia